EP1891229A2 - Method for identifying fungicidally active compounds that are based on ipp isomerases - Google Patents

Abstract

The invention relates to a method for identifying fungicides, to the use of fungal IPP isomerase for identifying fungicides, and to the use of inhibitors of the IPP isomerase as fungicides.

Description

A method of identifying fungicidally active compounds based on isopentenyl pyrophosphate isomerases

The invention relates to a method of identifying fungicides, the use of fungal isopentenyl pyrophosphate isomerase to identify fungicides, and the use of inhibitors of isopentenyl pyrophosphate isomerase as fungicides.

Undesirable fungus growth, which causes considerable damage to agriculture every year, can be controlled through the use of fungicides. The claims of fungicides have steadily increased in terms of their effectiveness, costs and above all their environmental compatibility. There is therefore a need for new substances or substance classes that can be developed into powerful and environmentally compatible new fungicides. In general, it is common to look for such new lead structures in greenhouse tests. However, such tests are labor intensive and expensive. The number of substances that can be tested in the greenhouse is limited accordingly. An alternative to such tests is the use of so-called high throughput screening (HTS). In an automated process, a large number of individual substances are tested for their effect on cells, individual gene products or genes. If an effect is detected for certain substances, they can be investigated in conventional screening methods and, if necessary, further developed.

Advantageous targets for fungicides are often sought in essential biosynthetic pathways. Ideal fungicides are also those substances which inhibit gene products which are of crucial importance in the expression of the pathogenicity of a fungus.

It was therefore an object of the present invention to identify and make available a suitable new target for potential fungicidally active compounds, and to provide a method which makes it possible to identify modulators of this point of attack which can then be used as fungicides.

Isopentenyl pyrophosphate isomerase (EC 5.3.3.2), also known as isopentenyl pyrophosphate Δ isomerase, isopentenyl diphosphate Δ isomerase, or methylbutenyl pyrophosphate isomerase, catalyzes the isomerization of the carbon double bond of isopentenyl pyrophosphate (IPP), with dimethylallyl pyrophosphate (DMAPP ) (Figure 1).

The isopentenyl pyrophosphate isomerase - hereinafter also abbreviated to IPP isomerase or IPPI - thus catalyzes an essential step of isoprenoid biosynthesis with more than 23,000 known metabolites. The synthetic route is described in all organisms and provides while different substance classes available. These include the sterols, carotenoids, dolichols, ubiquinones and prenylated proteins. The IPP isomerase catalyzes the critical activation step in the pathway that converts isopentenyl pyrophosphate (IPP) into the highly electrophilic isomer dimethyl-allyl-diphosphate (DMAPP). IPP and DMAPP are substrates for - prenyltransferases that synthesize polyisoprenoid chains.

In S. cerevisiae (an ascomycete) it could be shown that the corresponding gene IDI1 is essential and occurs only once in the genome. (Mayer et al., 1992).

The isoprenoid pathway occurs in all organisms and produces a variety of small, mostly lipophilic substances that perform a number of important functions. The sterols, components of eukaryotic membranes and hormones, the carotenes, photoreceptors during vision and photosynthesis, coenzymes during respiration, the molting hormones in insects, as well as the cytokinins, hormones in plants play an outstanding role. Isoprenoids are synthesized in two different phases. The first phase of the synthesis is the stepwise construction of hydroxymethylglutaryl-coenzyme A from three molecules of acetyl-CoA. This is reduced by HMG-CoA reductase to mevalonate and is condensed into squalene in a number of other reactions. Central to this first phase is the IPP isomerase, which provides both the isopentenyl phyrophosphate and the dimethylallyl phyrophosphate (Wouters et al., 2003). These two compounds are further condensed in a head to tail reaction to geranyl diphosphate. This can then be further processed in the metabolism depending on the organism to different products. For fungi, the synthesis of sterols is of essential importance.

The IPP isomerase is already known from a number of fungi (see also Figure 2). These include e.g. S. cerevisiae, S. pombe etc.

IPP isomerases are characterized by specific motifs at the amino acid level and can be identified, inter alia, from these motifs. For example, targeted mutagenesis in yeast has shown that two amino acids are essential. These are the amino acids Cys and GIn in positions 139 and 207 (S. cerevisiae, see also Fig. 2), embedded in the sequences CCSH and HEEDY, respectively (Street et al., 1994, Wouters et al, 2003).

Genes for the IPP isomerase have been cloned from various organisms, including from various yeasts such as Saccharomyces cerevisiae (Swissprot Accession No .: Pl 5496), Schizosaccharomyces pombe (Swissprot Accession No .: QI Ol 32), and Phaffia rhodozyma (Swissprot Accession No .: 042641). The sequence similarities are significant within the eukaryotic classes. It was another object of the present invention to identify new targets of fungicides in fungi, especially in phytopathogenic fungi, and to make available a method in which inhibitors of such a target or polypeptide can be identified and tested for their fungicidal properties. It was therefore an object of the present invention to examine whether the IPP isomerase of the plant pathogenic basidiomycete U. maydis is also an essential gene and leads to their removal to non-viable spores, and the IPP isomerase from phytopathogenic fungi is fundamentally suitable as a target for fungicides is.

The object has been achieved by isolating the IPP isomerase-encoding nucleic acid (ipil) from a phytopathogenic fungus, U. maydis, the polypeptide encoded therefrom (IPI1) and providing a method with which inhibitors of this enzyme are determined can. The inhibitors identified by this method can actually be used in vivo against fungi.

Description of the pictures

Figure 1: Schematic representation of the IPP isomerase-catalyzed isomerization of isopentenyl pyrophosphate to dimethylallyl pyrophosphate.

Figure 2: Comparison of the known IPP isomerase proteins from fungi and phytopathogenic fungi (UM = U. maydis, PC = P. chrysosporium, IDI1 = S. cerevisiae, ADL = A. gossypii, Idil = S. pombe, MG = M. grisea; CA = C. albicans; AN = A .. nidulans; FG = F. graminis; NC = N. crassa; PHYSO = P. soyae; PHYTRA = P. ramorum). Areas with identity or high homology are highlighted in gray

Figure 3: 12% Bis-Tris-SDS gel to demonstrate heterologous expression of U.maydis IPP isomerase in E. coli.

1 + 18 = marker; 2-13 = eluted fractions with 25 mM imidazole; 14-17 = eluted fractions with IM imidazole; 19 = cytoplasmic fraction; 20 = membrane fraction; 21 = flow; 22 + 23 = 1st and 2nd washings; 24 = Pooled fractions No. 6,7,8,9

Figure 4: Spore analog of the ipi-knock-out strains. Candidate spores were streaked on medium (PD medium) without (1A-4A, PD / Hyg medium) and with selection 1B-4B. If the switched-off gene is essential, no spores may grow on PD / Hyg medium if all spores are haploid. Again and again it happens that diploid spores are selected as candidates. Therefore, in all cases where spores grew on PD / Hyg medium, they were examined by PCR analysis. It was shown that these spores were diploid, so they still contained a copy of the ipi wild-type gene.

SEQ ID NO: 1 Nucleic acid sequence encoding the Ustilago maydis isopentenyl pyrophosphate isomerase.

SEQ ID NO: 2 amino acid sequence of the isopentenyl pyrophosphate isomerase from Ustilago maydis. definitions

The term "homology" or "identity" is intended to mean the number of matching amino acids (identity) with other proteins, expressed as a percentage. Preferably, the identity is determined by comparisons of a given sequence to other proteins using computer programs. If sequences that are compared to one another have different lengths, the identity must be determined in such a way that the number of amino acids which the shorter sequence has in common with the longer sequence determines the percentage of the identity. The identity can be determined by standard means of known and publicly available computer programs such as ClustalW (Thompson et al., Nucleic Acids Research 22 (1994), 4673-4680). ClustalW is publicly available, for example, from Julie Thompson (Thompson@EMBL-Heidelberg.DE) and Toby Gibson (Gibson@EMBL-Heidelberg.DE), European Molecular Biology Laboratory, Meyerhofstrasse 1, D 691 17 Heidelberg, Germany. ClustalW can also be found on various websites, including the IGBMC (Institut de Genetique et de Biologie Moleculaire et Cellulaire, BP163, 67404 Illkirch Cedex, France; ftp://ftp-igbmc.u-strasbg.fr/pub/) and the EBI ( ftp://ftp.ebi.ac.uk/pub/software/) as well as on all mirrored websites of the EBI (European Bioinformatics Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge CB10 ISD, UK). If the ClustalW computer program of version 1.8 is used to determine the identity between eg a given reference protein and other proteins, the following parameters should be set: KTUPLE = I, TOPDIAG = 5, WINDO W = 5, PAIRGAP = 3, GAPOPEN = IO, GAPEXTEND = 0.05, GAPDIST = 8, MAXDIV = 40, MATRDC = GONNET, ENDGAPS (OFF), NOPGAP, NOHGAP. One way to find similar sequences is to perform sequence database searches. Here, one or more sequences are specified as so-called query. This query sequence is then compared by means of statistical computer programs with sequences contained in the selected databases. Such database queries ("blast searches") are known to the person skilled in the art and can be carried out by various providers. If such a database query is carried out, for example, at the NCBI (National Center for Biotechnology Information, http://www.ncbi.nlm.nih.gov/), then the default settings that are specified for the respective comparison request should be used. For protein sequence comparisons ("blastp"), these are the following settings: Limit entrez = not activated; Filter = low complexity activated; Expect value = 10; word size = 3; Matrix = BLOSUM62; Gap costs: Existence = 11, Extension = 1. As a result of such a query, among other parameters, the proportion of identity between the query sequence and the similar sequences found in the databases is displayed. In the context of the present invention, a protein according to the invention should therefore be understood as meaning those proteins which when using at least one of the identity determination methods described above, have an identity of at least 70%, preferably of at least 75%, more preferably of at least 80%, more preferably of at least 85%, and especially of at least 90%.

The term "complete IPP isomerase" as used herein describes an IPP isomerase encoded by a complete coding region of a transcriptional unit comprising an ATG start codon and comprising all the information-bearing exon regions of the organism of origin, for an IPP Isomerase coding gene, as well as the necessary for a correct termination of transcription signals.

The term "biological activity of an IPP isomerase" as used herein refers to the ability of a polypeptide to undergo the reaction described above, i. to catalyze the isomerization of the carbon double bond of isopentenyl pyrophosphate and dimethylallyl pyrophosphate.

As used herein, the term "active fragment" describes no longer complete nucleic acids encoding IPP isomerase but which still encode polypeptides having the biological activity of an IPP isomerase, and the reaction characteristic of IPP isomerase, as above described catalyze. Such fragments are shorter than the above-described complete nucleic acids encoding IPP isomerase. In this case, nucleic acids may have been removed both at the 3 'and / or 5' ends of the sequence, but parts of the sequence may also be deleted, i. have been removed that do not affect the biological activity of IPP isomerase crucial. A lower or possibly also an increased activity, which still permits the characterization or use of the resulting IPP-isomerase fragment, is understood to be sufficient in the sense of the expression used here. The term "active fragment" may also refer to the amino acid sequence of IPP isomerase, and then applies analogously to the above for those polypeptides which no longer contain certain parts compared to the complete sequence defined above, but the biological activity of the enzyme is not is decisively impaired. The fragments can have different lengths.

The terms "IPP isomerase inhibition test" or "inhibition test" as used herein refer to a method or assay that allows inhibition of the enzymatic activity of a polypeptide having the activity of an EPP isomerase by one or more of the detect multiple chemical compounds (candidate compound (s)) whereby the chemical compound can be identified as an inhibitor of IPP isomerase. The term "gene" as used herein is the term for a portion of the genome of a cell responsible for the synthesis of a polypeptide chain.

The term "fungicidal" or "fungicidal" as used herein refers to chemical compounds which are suitable for controlling human, animal and phytopathogenic fungi, in particular phytopathogenic fungi. Such phytopathogenic fungi are named below, but the enumeration is not exhaustive:

Plasmodiophoromycetes, Oomycetes, Chytridiomycetes, Zygomycetes, Ascomycetes, Basidiomycetes and Deuteromycetes, e.g.

Pythium species such as Pythium ultimum, Phytophthora species such as Phytophthora infestans, Pseudoperonospora species such as Pseudoperonospora humuli or Pseudoperonospora cubensis, Plasmopara species such as Plasmopara viticola, Bremia species such as Bremia lactucae, Peronospora Species such as Peronospora pisi or P. brassicae, Erysiphe species such as Erysiphe graminis, Sphaerotheca species such as Sphaerotheca fuliginea, Podosphaera species such as Podosphaera leucotricha, Venturia species such as Venturia inaequalis, Pyrenophora species , such as, for example, Pyrenophora teres or P. graminea (conidia form: Drechslera, Syn: Helminthosporium), Cochliobolus species, such as Cochliobolus sativus (conidia form: Drechslera, Syn: Helminthosporium), Uromyces species, such as, for example, Uromyces appendiculatus, Puccinia species , such as Puccinia recondita, Sclerotinia-Ar such as Sclerotinia sclerotiorum, Tilletia species such as Tilletia caries; Ustilago species such as Ustilago nύda or Ustilago avenae, Pellicularia species such as Pellicularia sasakii, Pyricularia species such as Pyricularia oryzae, Fusarium species such as Fusarium culmorum, Botrytis species, Septoria species such as Septoria nodorum, Leptosphaeria species such as Leptosphaeria nodorum, Cercospora species such as Cercospora canescens, Alternaria species such as Alternaria brassicae or Pseudocercosporella species such as Pseudocercosporella herpotrichoides.

Of particular interest are e.g. also Magnaporthe grisea, Cochliobulus heterostrophus, Nectria hematococcus and Phytophthora species.

However, fungicidal active substances which are found with the help of the IPP isomerases according to the invention from phytopathogenic fungi can also interact with IPP isomerase from human pathogenic fungus species, the interaction with the different IPP isomerases occurring in these fungi not always having to be equally strong. The subject of the present invention is therefore also the use of inhibitors of IPP isomerase for the production of agents for the treatment of diseases caused by human pathogenic fungi.

The following human pathogenic fungi are of particular interest, which can cause the following diseases:

Dermatophytes, e.g. Trichophyton spec, Microsporum spec, Epidermophyton floccosum or Keratomyces ajelloi, which are e.g. Cause foot mycoses (tinea pedis),

Yeasts, e.g. Candida albicans causing thrush oesophagitis and dermatitis, Candida glabrata, Candida krusei or Cryptococcus neoformans, which are e.g. can cause pulmonary cryptococcosis and also

Molds, such as Aspergillus fumigatus, A. flavus, A. niger, e.g. bronchopulmonary aspergillosis or fungal sepsis, Mucor spec, Absidia spec, or Rhizopus spec. Cause zygomycoses (intravascular mycoses), Rhinosporidium seeberi, e.g. chronic granulomatous pharyngitis and tracheitis, Madurella myzetomatis, e.g. subcutaneous mycetomas, Histoplasma capsulatum, which is e.g. reticuloendothelial cytomycosis and M. darling causes, Coccidioides immitis, the z. Pulmonary coccidioidomycosis and sepsis, Paracoccidioides brasiliensis, e.g. causes Brazilian blastomycosis, Blastomyces dermatitidis, e.g. Gilchrist's disease and North American blastomycosis, Loboa loboi, e.g. Keloid blastomycosis and Lobo's disease, and Sporothrix schenckii, which causes e.g. Sporotrichosis (granulomatous skin mycosis) causes.

Fungicidal agents, which are found with the help of one of a specific fungus, here from Ustilago maydis, IPP isomerase obtained, so can also interact with IPP isomerase from other numerous fungal species, especially with phytopathogenic fungi, the interaction with the different in these fungi occurring IPP isomerase does not always have to be the same strength. This explains, inter alia, the observed selectivity of the substances active on this enzyme.

The term "homologous promoter" as used herein refers to a promoter which controls the expression of the gene in question in the original organism. As used herein, the term "heterologous promoter" refers to a promoter that has other properties than the promoter that controls expression of the subject gene in the parent organism. The term "competitor" as used herein refers to the property of the compounds to compete with other, optionally identifiable compounds for binding to the IPP isomerase and to displace or displace it from the enzyme.

As used herein, the term "inhibitor" refers to a substance that directly inhibits an enzymatic activity of the IPP isomerase. Such an inhibitor is preferably "specific", i. it selectively inhibits IPP isomerase activity at a concentration lower than the concentration of inhibitor needed to elicit a different, unrelated effect. Preferably, the concentration is two fold lower, more preferably fivefold lower, and most preferably at least tenfold or fifty times lower than the concentration of a compound needed to produce a nonspecific effect.

The term "modulator" as used herein is a generic term for inhibitors and activators. Modulators may be small organic chemical molecules, peptides or antibodies that bind to or influence the activity of the polypeptides of the invention. Furthermore, modulators may be small organic chemical molecules, peptides or antibodies which bind to a molecule which, in turn, binds to the polypeptides of the invention and thereby affects their biological activity. Modulators may be natural substrates and ligands or structural or functional mimetics thereof. Preferably, however, the term "modulator" as used herein refers to those molecules that are not the natural substrates or ligands.

Description of the invention

In the present invention, the complete sequence of an IPP isomerase from the plant pathogenic fungus Ustilago maydis is provided for the first time, the other

Research on EPP isomerases, in particular from phytopathogenic fungi, thus enabling the closure of a new target protein for the identification of new fungicides.

Research on IPP isomerase has so far been limited primarily to its pharmacological importance (Cheng and Oldfield, 2004, Thompsom et al, 2002, Rohdich et al., 2004). In this case, inhibitors of this enzyme have also been processed, which are to find a pharmaceutical application. Inhibitors of IPP isomerase, such as natural inhibitors or transition state analogs of the IPP isomerase substrate have been described (Wouters et al., 2003).

However, despite extensive research on IPP isomerase, it was previously unknown that the fungi IPP isomerase may be a target protein (a so-called "target") of fungicidally active substances. Thus, it is shown for the first time in the present invention that the IPP isomerase is an enzyme which is particularly important for fungi and is therefore particularly suitable for use as a target protein for the search for further and improved fungicidally active compounds.

Inhibitors of the IPP isomerase with a fungicidal activity have not previously been described. It is known that the enzyme is essential in S. cerevisiae (Mayer et al., 1992). However, none of the publications comment on whether the fungal enzyme affects IPP isomerase, particularly in phytopathogenic fungi, by drugs, e.g. can be inhibited, and whether the control of fungi, in particular phytopathogenic fungi, in vivo with an IPP isomerase modulating agent is possible. The IPP isomerase has thus far not been described as a target protein for fungicides. There are no known active substances which have a fungicidal action and whose site of action is the IPP isomerase.

In the context of the present invention, it has now been possible to show that the IPP isomerase in the case of phytopathogenic fungi can be a point of attack or "target" for fungicidal active substances, ie inhibition of the IPP isomerase could lead to damage or death of the fungus. Thus, in the phytopathogenic fungus Ustilago maydis, a gene coding for an IPP isomerase according to SEQ ID NO: 1 was identified (ipil). The knockout of this gene proved lethal. No viable knockout spores were obtained from U. maydis. In further experiments directed to the accessibility of the IPP isomerase to drugs in vitro and also in vivo, the enzyme IPP isomerase could be further determined to be a polypeptide can be used to identify modulators or inhibitors of its enzymatic activity in suitable test methods, which is not self-evident in the case of various theoretically interesting targets.

In the context of the present invention, therefore, a method has been developed which is suitable for determining the activity of the IPP isomerase and the inhibition of this activity in a so-called inhibition test, in this way inhibitors of the enzyme, e.g. in HTS and UHTS processes and to test their fungicidal properties. In the context of the present invention, it has also been shown that the inhibitors of fungi IPP isomerase can be used as fungicides.

In the context of the present invention, it has also been found that the IPP isomerase can also be inhibited in vivo by active ingredients and a fungal organism treated with these active substances can be damaged and killed by the treatment with these active substances. The inhibitors of a fungal IPP isomerase can therefore be used as fungicides in crop protection or as antimycotics in pharmaceutical indications. In the present invention, it is shown, for example, that the inhibition of IPP isomerase with a substance identified in a method according to the invention leads to the death of the treated fungi in synthetic media or on the plant.

The IPP isomerase can be obtained from various phytopathogenic or even human or animal pathogenic fungi, e.g. from mushrooms such as the phytopathogenic fungus U. maydis. For the production of the IPP isomerase from fungi, the gene may be e.g. recombinantly expressed in Escherichia coli and an enzyme preparation is prepared from E. coli cells (Example 1). Preference is given to using IPP isomerases from phytopathogenic fungi in order to identify fungicides which can be used in crop protection. If the goal is the identification of fungicides or antimycotics that are to be used in pharmaceutical indications, the use of IPP isomerases from human or animal pathogenic fungi is recommended.

Thus, for the expression of the ipil-encoded polypeptide IPI1 from U. maydis, the associated ORF was amplified by means of PCR by methods known to those skilled in the art via selected primers. The corresponding DNA was cloned into the expression vector pET21b such that the IPI1 protein is expressed with a Hisβ tag. For the expression of the IPI1 the plasmid was transformed into E. coli BL21 (DE3) and the polypeptide according to example 1 was recovered.

The present invention thus also provides a complete genomic sequence of a phytopathogenic fungus coding for an IPP isomerase, and the Use or the use of the encoded polypeptide for the identification of inhibitors of the enzyme described.

The present invention therefore also relates to the nucleic acid coding for a polypeptide having the enzymatic function of an IPP isomerase according to SEQ ID NO: 1 from the fungus Ustilago maydis.

Because of the homologies (see also Fig. 2) present in species-specific nucleic acids encoding IPP isomerases, IPP isomerases from other plant pathogenic fungi can also be identified and used to accomplish the above object, i. they may also be used to identify inhibitors of an IPP isomerase, which in turn may be used as fungicides in crop protection. However, it is also conceivable to use another fungus which is not phytopathogenic, or to use its IPP isomerase or the sequence coding therefor, in order to identify fungicidal inhibitors of the IPP isomerase. Because of the sequence given here according to SEQ ID NO: 1 and any primers derived therefrom and optionally with the aid of the consensus sequence sections shown in FIG. 2, in particular the above-mentioned (amino acid) sequence sections "CCSH" and "HEIDY", it is possible for a person skilled in the art to eg to obtain and identify further nucleic acids coding for IPP isomerases from other (phytopathogenic) fungi by PCR or to assign existing nucleic acid or amino acid sequences. Such nucleic acids and their use in methods of identifying fungicidal agents are considered to be encompassed by the present invention.

With the aid of the nucleic acid sequence according to the invention as well as sequences obtained from other phytopathogenic fungi according to the methods described above, further nucleic acid sequences coding for an IPP isomerase from other fungi can be identified.

The present invention therefore relates to nucleic acids from phytopathogenic fungi which code for a polypeptide having the enzymatic activity of an IPP isomerase, in particular polypeptides comprising the motif described above.

The present invention preferably relates to nucleic acids from the phytopathogenic fungal species mentioned above under Defintionen, which code for a polypeptide with the enzymatic activity of an EPP isomerase. The present invention particularly preferably relates to the nucleic acid coding for the Ustilago maydis IPP isomerase with the SEQ ID NO: 1 as well as the nucleic acids coding for the polypeptides according to SEQ ID NO: 2 or active fragments thereof.

The nucleic acids according to the invention are, in particular, single-stranded or double-stranded deoxyribonucleic acids (DNA) or ribonucleic acids (RNA). Preferred embodiments are fragments of genomic DNA, and cDNAs.

The nucleic acids according to the invention particularly preferably comprise a sequence of phytopathogenic fungi coding for a polypeptide having the enzymatic activity of an IPP isomerase selected from

a) a sequence according to SEQ ID NO: 1,

b) sequences which code for a polypeptide which comprises the amino acid sequence according to SEQ ID NO: 2,

c) sequences which hybridize to the sequences defined under a) and b) at a hybridization temperature of 42-65 ° C,

d) sequences which have at least 80%, preferably at least 85% and more preferably at least 90% identity with the sequences defined under a) and b), and

e) sequences which are complementary to the sequences defined under a) to d).

As already stated above, the present invention is not limited only to the Ustilago maydis IPP isomerase. In an analogous manner known to those skilled in the art, it is also possible to obtain from other fungi, preferably from phytopathogenic fungi, polypeptides having the activity of an IPP isomerase, which are then oxidized, for example. can be used in a method according to the invention. Preferably, the IPP isomerase from Ustilago maydis is used.

The present invention furthermore relates to DNA constructs which comprise a nucleic acid according to the invention and a homologous or heterologous promoter.

The choice of heterologous promoters depends on whether pro- or eukaryotic cells or cell-free systems are used for expression. Examples of heterologous promoters are the 35S promoter of cauliflower mosaic virus for plant cells, the alcohol dehydrogenase promoter for yeast cells, the T3, T7 or SP6 promoters for prokaryotic cells or cell-free systems. Fungal expression systems, such as, for example, the Pichia pastoris system should preferably be used, in which case the transcription is driven by the methanol-inducible AOX promoter.

The present invention furthermore relates to vectors which contain a nucleic acid according to the invention, a regulatory region according to the invention or a DNA construct according to the invention. As vectors all phages used in molecular biology laboratories, plasmids, phagemids, phasmids, cosmids, YACs, BACs, artificial chromosomes or particles suitable for particle bombardment can be used.

Preferred vectors are e.g. the p4XXprom. Vector series (Mumberg et al., 1995) for yeast cells, pSPORT vectors (Life Technologies) for bacterial cells, or the Gateway vectors (Life Technologies) for various expression systems in bacterial cells, plants, P. pastoris, S. cerevisiae or insect cells.

The present invention also provides host cells which contain a nucleic acid according to the invention, a DNA construct according to the invention or a vector according to the invention.

The term "host cell" as used herein refers to cells that naturally do not contain the nucleic acids of the invention.

Suitable host cells are both prokaryotic cells, preferably E. coli, and eukaryotic cells, such as cells of Saccharomyces cerevisiae, Pichia pastoris, insects, plants, frog oocytes and mammalian cell lines.

The present invention furthermore relates to polypeptides having the biological activity of an IPP isomerase which are encoded by the nucleic acids according to the invention.

The polypeptides according to the invention preferably comprise an amino acid sequence selected from plant-pathogenic fungi

(a) the sequence according to SEQ ID NO: 2,

(b) sequences which have at least 80%, preferably at least 85%, particularly preferably 90% and especially preferably 95% identity with the sequence defined under a),

(c) fragments of the sequences indicated under a) or b) which have the same biological activity as the sequence defined under a). The term "polypeptides" as used herein refers to both short amino acid chains, commonly referred to as peptides, oligopeptides or oligomers, and longer amino acid chains, commonly referred to as proteins. It includes amino acid chains which may be modified either by natural processes such as post-translational processing or by prior art chemical methods. Such modifications may occur at various sites and multiply in a polypeptide, such as at the peptide backbone, at the amino acid side chain, at the amino and / or at the carboxy terminus. They include, for example, acetylations, acylations, ADP ribosylations, amidations, covalent linkages with flavins, heme fractions, nucleotides or nucleotide derivatives, lipids or lipid derivatives or phosphatidylinositol, cyclizations, disulfone bridge formations, demethylations, cystine formations, formylations, gamma-carboxylations, glycosylations, hydroxylations, iodinations, methylations, myristolations, oxidations, proteolytic processing, phosphorylations, selenoylations and tRNA-mediated additions of amino acids.

The polypeptides of the invention may be in the form of "mature" proteins or as part of larger proteins, e.g. as fusion proteins. Furthermore, they may have secretion or "leader" sequences, pro-sequences, sequences that allow easy purification, such as multiple histidine residues, or additional stabilizing amino acids. The proteins according to the invention can also be present as they are naturally present in their organism of origin, from which they can be obtained directly, for example. Active fragments of an EPP isomerase can also be used in the methods according to the invention, as long as they allow the determination of the enzymatic activity of the polypeptide or its inhibition by a candidate compound.

The polypeptides used in the methods of the invention may have deletions or amino acid substitutions as compared to the corresponding regions of naturally occurring IPP isomerases, as long as they still show at least the biological activity of a complete IPP isomerase. Conservative substitutions are preferred. Such conservative substitutions include variations wherein one amino acid is replaced by another amino acid from the following group:

1. Small aliphatic, non-polar or slightly polar residues: Ala, Ser, Thr, Pro and Gly;

2. Polar, negatively charged residues and their amides: Asp, Asn, Glu and GIn;

3. Polar, positively charged residues: His, Arg and Lys; 4. Large aliphatic, non-polar residues: Met, Leu, He, VaI and Cys; and

5. Aromatic radicals: Phe, Tyr and Trp.

One possible EPP isomerase purification procedure is based on preparative electrophoresis, FPLC, HPLC (e.g., using gel filtration, reverse phase or slightly hydrophobic columns), gel filtration, differential precipitation, ion exchange chromatography, or affinity chromatography (see Example 2).

A rapid method for isolating EPP isomerase synthesized by host cells begins with the expression of a fusion protein, whereby the fusion partner can be easily affinity-purified. For example, the fusion partner may be an MBP tag. The fusion protein can then be purified on amylose resin. The fusion partner can be separated by partial proteolytic cleavage, for example, on linkers between the fusion partner and the polypeptide of the invention to be purified. The linker can be designed to include target amino acids, such as arginine and lysine residues, that define sites for cleavage by trypsin. To generate such linkers, standard cloning methods using oligonucleotides can be used.

Further possible purification procedures are again based on preparative electrophoresis, FPLC, HPLC (e.g., using gel filtration, reverse phase or slightly hydrophobic columns); Gel filtration, differential precipitation, ion exchange chromatography and affinity chromatography.

The terms "isolation or purification" as used herein mean that the polypeptides of the invention are separated from other proteins or other macromolecules of the cell or tissue. Preferably, a composition containing the polypeptides according to the invention is at least 10-fold and particularly preferably at least 100-fold enriched in protein content compared to a preparation from the host cells.

The polypeptides according to the invention can also be affinity-purified without fusion partners with the aid of antibodies which bind to the polypeptides.

The process for producing polypeptides having the activity of an IPP isomerase, e.g. the polypeptide IPIII from U. maydis, is characterized by

(a) culturing a host cell containing at least one expressible nucleic acid sequence encoding a polypeptide of fungi with the biological Activity of an IPP isomerase under conditions that ensure the expression of this nucleic acid, or

(b) expressing an expressible nucleic acid sequence encoding a polypeptide of fungi having the biological activity of an IPP isomerase in an in v / Yro system, and

(c) recovering the polypeptide from the cell, the culture medium or the in vitro system.

The cells thus obtained containing the polypeptide of the present invention or the purified polypeptide thus obtained are suitable for use in methods of identifying modulators of IPP isomerase.

The present invention also provides the use of polypeptides from fungi, preferably from phytopathogenic fungi, which exert at least one biological activity of an IPP isomerase, in methods for identifying fungicides, wherein the inhibitors of IPP isomerase can be used as fungicides. The IPP isomerase from Ustilago maydis is particularly preferably used.

Fungicidal agents, which are found by means of an IPP isomerase from a certain fungal species and based on a method according to the invention, can also interact with IPP isomerase from other fungal species, the interaction with the different present in these fungi IPP isomerase is not always the same must be strong. This explains, among other things, the selectivity of effective substances. The use of the active ingredients found with a specific IPP isomerase as a fungicide in other fungi can be attributed to the fact that IPP isomerases from different fungal species are close to each other and show clear homology in larger areas. Thus, it is clear from Figure 2 that such homology exists over significant sequence segments between S. cerevisiae, S. pombe, and U. maydis, thus diminishing the effect of e.g. is not restricted to U. maydis with the aid of the U. maydis IPP isomerase.

The present invention therefore also provides a method for identifying fungicides by testing potential inhibitors or modulators of the enzymatic activity of the IPP isomerase (candidate compound or test compound) in an IPP isomerase inhibition test, wherein an inhibitor or inhibitor found in an activity test is Modulater of IPP isomerase can then be tested for its effectiveness as a fungicide in vivo, ie on a fungus. Methods which are suitable for identifying modulators, in particular inhibitors or antagonists of the polypeptides according to the invention, are generally based on the determination of the activity or biological functionality of the polypeptide. In principle both whole-cell-based methods (in vivo methods) and methods based on the use of the polypeptide isolated from the cells, which may be present in purified or partially purified form or else as crude extract, are suitable. These cell-free in vitro methods can be used as well as in vivo methods on a laboratory scale, but preferably also in HTS or UHTS methods. Following in vivo or in vitro identification of polypeptide modulators, assays on fungal cultures may be performed to assess the fungicidal activity of the compounds found.

Many test systems that aim to test compounds and natural extracts are preferably designed for high throughput rates to maximize the number of substances tested in a given time period. Test systems based on cell-free work need purified or semi-purified protein. They are suitable for a "first" test, which primarily aims to detect a possible influence of a substance on the target protein. If such a first test has been carried out and one or more compounds, extracts, etc. found, the effect of such compounds in the laboratory can be investigated even more targeted. Thus, in a first step, the inhibition or activation of the polypeptide of the invention in vitro can be checked again, in order subsequently to test the efficacy of the compound on the target organism, here one or more phytopathogenic fungi. The compound may then optionally be used as a starting point for the further search and development of fungicidal compounds based on the original structure, but e.g. are optimized in terms of efficacy, toxicity or selectivity.

In order to find modulators, e.g. a synthetic reaction mix (e.g., products of in vitro transcription) or a cellular component such as a membrane, compartment, or any other preparation containing the polypeptides of the invention, together with an optionally labeled substrate or ligand of the polypeptides in the presence and

Absence of a candidate molecule are incubated. The ability of the candidate molecule to inhibit the enzymatic activity of the polypeptides of the invention is e.g. Recognizable from a reduced binding of the optionally labeled ligand or at a reduced

Reaction of the optionally labeled substrate. Molecules which inhibit the biological activity of the polypeptides of the invention are good antagonists or inhibitors.

The detection of the biological activity of the polypeptides according to the invention can be improved by a so-called reporter system. Reporter systems in this regard are but not limited to colorimetric or fluorimetric detectable substrates that are converted to a product or a reporter gene that responds to changes in the activity or expression of the polypeptides of the invention or other known binding assays.

Another example of a method by which modulators of the polypeptides of the invention can be found is a displacement assay which comprises subjecting the polypeptides of the invention and a potential modulator to a molecule known to bind to the polypeptides of the invention, such as a natural one, under suitable conditions Substrate or ligands or a substrate or ligand mimetic. The polypeptides of the invention themselves can be labeled, e.g. fluorimetric or colorimetric, so that one can accurately determine the number of polypeptides that are bound to a ligand or have undergone a reaction. Likewise, however, the binding can be monitored by means of the optionally labeled substrate, ligands or substrate analogues. In this way, the effectiveness of antagonists can be measured.

Effects such as cell toxicity are usually ignored in these in vitro systems. The test systems check both inhibitory or suppressive effects of the substances, as well as stimulatory effects. The effectiveness of a substance can be checked by concentration-dependent test series. Control approaches without test substances or without enzyme can be used to evaluate the effects.

The host cells containing nucleic acids encoding nucleic acid encoding IPP isomerase useful in the present invention also allow the development of cell-based assays to identify substances that modulate the activity of the polypeptides of the present invention.

Preferably, the modulators to be identified are small organic chemical compounds, but not the natural inhibitors of the enzyme, e.g. Ligands of the enzyme or substrate analogs to form inorganic or nonspecific inhibitors that generally destroy or reduce the activity of an enzyme, e.g. by the nonspecific disruption of the protein structure or the reaction with reactive amino acids of the protein.

A method for identifying a compound which modulates the activity of an IPP isomerase from fungi and which can be used as a fungicide in plant protection is therefore preferred in that one

a) a polypeptide according to the invention or a host cell containing this polypeptide with a chemical compound or with a mixture of chemical compounds under conditions which allow the interaction of a chemical compound with the polypeptide,

b) compares the activity of the polypeptide of the invention in the absence of a chemical compound with the activity of the polypeptide of the invention in the presence of a chemical compound or a mixture of chemical compounds, and

c) selecting the chemical compound that specifically modulates, preferably inhibits, the activity of the polypeptide of the invention, and optionally

d) tests the fungicidal activity of the selected compound in vivo.

The compound which specifically inhibits the activity of the polypeptide according to the invention is particularly preferably determined. The term "activity" as used herein refers to the biological activity of the polypeptide of the invention.

In one embodiment, which is based on a known assay for the determination of IPP isomerase, the reaction catalyzed by the IPP isomerase is coupled with the reaction of isopentenyltransferase. This enzyme catalyzes the reaction of dimethylallyl pyrophosphate and AMP to isopentenyladenine and pyrophosphate. The pyrophosphate is further degraded by the enzyme pyrophosphatase. The resulting ^'phosphate may be known to the skilled person with a malachite green assay are determined. The experimental approach can be illustrated schematically as follows:

Isopentenyl pyrophosphate <=> dimethylallyl pyrophosphate

Isopentenyl transferase

Dimethylallyl pyrophosphate + AMP -> isopentenyladenine + PPj

pyrophosphatase

The measurement of the enzymatic activity of the IPP isomerase or the inhibition of this enzymatic activity by an inhibitor then takes place on the basis of the phosphate concentration. In this case, the lower or inhibited activity of the polypeptide according to the invention is monitored on the basis of the lower phosphate concentration relative to a control batch. It has surprisingly been found in the context of the present invention that the detection reagent malachite green from the product, but not from the substrate of the IPP isomerase directly release phosphate and can detect. Therefore, in a particularly preferred embodiment of the method described, both isopentyl transferase and pyrophosphatase (IPPase) can be dispensed with.

Other possibilities for determining the enzymatic activity of IPP isomerase are described inter alia in Ramos-Valdivia (1997) and are expressly intended to be part of the present application.

The measurement may also be done in more common formats for HTS or UHTS assays, e.g. in microtiter plates in which e.g. a total volume of 5 to 50 ul per batch or per well is presented. Thereby, the compound (candidate molecule) to be tested, potentially inhibiting or activating the activity of the enzyme (e.g. in a suitable concentration in

Test buffer submitted. Then the polypeptide according to the invention is added in the abovementioned test buffer and the reaction is started therewith. The batch is then incubated at a suitable temperature, e.g. measured the concentration of the resulting pyrophosphate.

Another measurement is carried out in a similar approach, but without the addition of a candidate molecule and without the addition of a polypeptide of the invention (negative control). Another measurement is again in the absence of a candidate molecule, but in the presence of the polypeptide of the invention (positive control). Negative and positive controls thus give the comparison values to the approaches in the presence of a candidate molecule.

With the method according to the invention inhibitors of IPP isomerase could be identified in this way.

It goes without saying that in addition to the abovementioned methods for determining the enzymatic activity of an IPP isomerase or the inhibition of this activity and for identifying fungicides, other, e.g. already known, methods or inhibition tests can be used, as long as these methods allow to determine the activity of an IPP isomerase and to detect an inhibition of this activity by a candidate compound.

In the context of the present invention, it has also been found that the inhibitors of an IPP isomerase according to the invention identified by means of a method according to the invention are suitable for damaging or killing fungi in a suitable formulation.

For this purpose, for example, a solution of the active substance to be tested can be pipetted into the wells of microtiter plates. After the solvent is evaporated, becomes each Cavity medium added. The medium is previously mixed with a suitable concentration of spores or mycelium of the fungus to be tested. The resulting concentrations of the active ingredient are, for example, 0.1, 1, 10 and 100 ppm.

The plates are then incubated on a shaker at a temperature of 22 ⁰ C until a sufficient growth is observed in the untreated control.

The evaluation is carried out photometrically at a wavelength of 620 nm. From the measurement data of the various concentrations, the drug dose can be determined, which leads to a 50% inhibition of fungal growth compared to the untreated control (ED ₅₀ ).

The present invention therefore also relates to the use of modulators of the IPP isomerase from fungi, preferably from phytopathogenic fungi as fungicides, or to methods for controlling preferably phytopathogenic fungi, characterized in that a modulator, preferably an inhibitor of an IPP Isomerase with the relevant fungus and / or its environment in an effective amount brings into contact.

The present invention also relates to fungicides identified by means of a method according to the invention.

The present invention therefore also relates to methods for identifying fungicides and to the use of inhibitors of TPP isomerase from fungi, preferably from phytopathogenic fungi as fungicides. Of these, however, natural inhibitors such as analogs of the substrate of the IPP isomerase or analogs of the transition state of the substrate and non-specific inhibitors, which also show a significant inhibitory effect in enzymes other than IPP isomerase or in principle have an inhibitory effect by damaging the protein structure , and inorganic compounds are not included. A specific inhibitor should have at least 10 times, preferably 20 times, particularly preferably 50 times and preferably 100 times more, an inhibitory effect on the IPP isomerase than on another enzyme.

The present invention also relates to fungicides which are identified by means of a method according to the invention.

Compounds which are identified by means of a method according to the invention and which have a fungicidal action due to the inhibition of the fungal IPP isomerase can thus be used for the preparation of fungicidal agents. Depending on their respective physical and / or chemical properties, the identified active compounds can be converted into the customary formulations, such as solutions, emulsions, suspensions, powders, foams, pastes, granules, aerosols, very fine encapsulations in polymeric substances and in seed coating compositions, and ULV-KaIt and warm mist formulations.

These formulations are prepared in a known manner, e.g. by mixing the active compounds with extenders, that is to say liquid solvents, liquefied gases under pressure and / or solid carriers, if appropriate using surface-active agents, that is to say emulsifiers and / or dispersants and / or foam-forming agents. In the case of using water as an extender, e.g. also organic solvents can be used as auxiliary solvents. Suitable liquid solvents are essentially: aromatics, such as xylene, toluene or alkylnaphthalenes, chlorinated aromatics or chlorinated aliphatic hydrocarbons, such as chlorobenzenes, chloroethylenes or methylene chloride, aliphatic hydrocarbons, such as cyclohexane or paraffins, e.g. Petroleum fractions, alcohols, such as butanol or glycol, and their ethers and esters, ketones, such as acetone, methyl ethyl ketone, methyl isobutyl ketone or cyclohexanone, strongly polar solvents, such as dimethylformamide and dimethyl sulfoxide, and water. By liquefied gaseous diluents or carriers are meant those liquids which are gaseous at normal temperature and under normal pressure, e.g. Aerosol propellants, such as halogenated hydrocarbons as well as butane, propane, nitrogen and carbon dioxide. Suitable solid carriers are: e.g. ground natural minerals, such as kaolins, clays, talc, chalk, quartz, attapulgite, montmorillonite or diatomaceous earth, and ground synthetic minerals, such as finely divided silica, alumina and silicates. Suitable solid carriers for granules are: e.g. Cracked and fractionated natural rocks such as calcite, marble, pumice, sepiolite, dolomite and synthetic granules of inorganic and organic flours and granules of organic material such as sawdust, coconut shells, corn cobs and tobacco stems. Suitable emulsifiers and / or foam-formers are: e.g. nonionic and anionic emulsifiers, such as polyoxyethylene fatty acid esters, polyoxyethylene fatty alcohol ethers, e.g. Alkylaryl polyglycol ethers, alkyl sulfonates, alkyl sulfates, aryl sulfonates and protein hydrolysates. Suitable dispersants are: e.g. Lignin-sulphite liquors and methylcellulose.

Adhesives such as carboxymethyl cellulose, natural and synthetic powdery, granular or latex polymers may be used in the formulations, such as gum arabic, polyvinyl alcohol, polyvinyl acetate, as well as natural phospholipids such as cephalins and lecithins, and synthetic phospholipids. Other additives may be mineral and vegetable oils. Dyes such as inorganic pigments such as iron oxide, titanium oxide, ferrocyan blue and organic dyes such as alizarin, azo and metal phthalocyanine dyes and trace nutrients such as salts of iron, manganese, boron, copper, cobalt, molybdenum and zinc can be used.

The formulations generally contain between 0.1 and 95% by weight of active ingredient, preferably between 0.5 and 90%.

The active compounds according to the invention, as such or in their formulations, can also be used in admixture with known fungicides, bactericides, acaricides, nematicides or insecticides, so as to obtain e.g. to broaden the spectrum of action or to prevent development of resistance. In many cases synergistic effects, i. E. the effectiveness of the mixture is greater than the effectiveness of the individual components.

When using the compounds according to the invention as fungicides, the application rates can be varied within larger ranges depending on the application.

According to the invention, all plants and parts of plants can be treated. In this context, plants are understood as meaning all plants and plant populations, such as desired and undesired wild plants or crop plants (including naturally occurring crop plants). Crop plants can be plants that can be obtained by conventional breeding and optimization methods or by biotechnological and genetic engineering methods or combinations of these methods, including the transgenic plants and including the protected by plant breeders' rights or non-protectable plant varieties. Plant parts are to be understood as meaning all aboveground and subterranean parts and organs of the plants, such as shoot, leaf, flower and root, examples of which include leaves, needles, stems, stems, flowers, fruiting bodies, fruits and seeds, and roots, tubers and rhizomes. The plant parts also include crops and vegetative and generative propagation material, such as cuttings, tubers, rhizomes, offshoots and seeds.

The treatment according to the invention of the plants and plant parts with the active ingredients is carried out directly or by acting on their environment, habitat or storage space according to the usual treatment methods, e.g. by dipping, spraying, vaporizing, atomizing, spreading, spreading and in propagation material, in particular in seeds, further by single or multi-layer wrapping.

The following examples illustrate various aspects of the present invention and are not intended to be limiting. Examples

example 1

Cloning, expression and purification of the IPII from U. maydis

For the heterologous expression of the ipil gene, the gene with the gene-specific oligonucleotides Idi-c (5 '-CTCGAGGATCCAGGAGGCGGTGAATG-S') and Idi-n (5'-CTCGCATATGTCGACCGCCACCGTCAC-3 ') was amplified by PCR and introduced via the introduced Ndel and ßαmFfl interface introduced into the vector pET21b (Novagen). The resulting plasmids were transformed into E. co / z ^'strain BL21 (DE3).

5 ml selection medium (dYT medium with 100 ug / ml ampicillin) was inoculated with a single colony and incubated at 37 ⁰ C overnight in a shaker. A glycerol stock culture was prepared as follows: 900μl culture and 100 ul of sterile glycerol mix and freezing at -70 ⁰ C. When

Preculture was inoculated 12 ml of dYT medium with 25 ul from the permanent culture and at 37 ° C over

Incubated overnight in a shaker. The major culture was seeded 1:40, i. 12 ml preculture and

500 ml dYT medium + 100 μg / ml ampicillin. The growth of the culture was carried out at 37 ⁰ C with shaking and after reaching an OD ₆ oo of 0.8, the culture by addition of ImM IPTG

(Final concentration) induced. After an incubation period of 5 hours at 37 ° C, the

Cells were harvested by centrifugation and frozen pellet at -70 ^0C.

The cell pellet of a 500 ml expression culture was resuspended in 35 ml of digestion buffer (50 mM Tris, 1% glycerol, ImM DTT, 300 mM NaCl, 0.5% Tween 20, pH 7.5). The digestion of the cells was carried out with a Sonifizierstab on ice. It was sonicated 8 times 45 seconds with 45 seconds break. The soluble and insoluble fractions were analyzed by Abzentri- fugieren (30 min. At 4 ⁰ C and 10 000 rpm) separately. The supernatant was bound to a 50% Ni-NTA-agarose matrix by Qiagen for 60 minutes at 4 ⁰ C and transferred to a blank column. The binding capacity of the Ni-NTA matrix is 9 mg protein per 1 ml agarose. The column was washed twice with 44 ml of digestion buffer + 10 mM imidazole. Elution was carried out in 2 ml fraction steps with digestion buffer + 250 mM imidazole. The fractions containing the purified enzyme were then pooled and diluted to 1 mg / ml. There was an addition of glycerol in a final concentration of 10%. The storage of the enzyme takes place at -7O ⁰ C. Example 2

Identification of modulators of IPP isomerase in an inhibition assay

The tests were performed in 384 MTPs from Greiner (transparent). The negative control was done by omitting the enzyme. 5 μl of RI buffer (10 mM Tris / HCl pH 7.5, 20 mM MgCl ₂ , 10% glycerol) or the substance to be tested (1/10 of the assay volume) were mixed with 20 μl substrate solution (0.15 mM IPP in reaction buffer RI), 25 .mu.l enzyme mix (0.59 ug / ml of purified protein (IPP isomerase) in reaction buffer Rl) at 37 ⁰ C for 25 minutes. 50 μl malachite green staining solution was added and incubated at RT for 90 minutes. The detection of a change in absorption took place at 620 nm.

Example 3

Detection of the fungicidal activity of the identified inhibitors of IPP isomerase

In the wells of microtiter plates, a methanolic solution of the identified by a process according to the invention active ingredient (Example 3), mixed with an emulsifier, pipetted. After the solvent has evaporated, 200 μl of Potato Dextrose Medium are added per well. The medium is previously mixed with appropriate concentrations of spores or mycelia of the fungus to be tested.

The resulting concentrations of the active ingredient are 0.1, 1, 10 and 100 ppm. The resulting concentration of the emulsifier is 300 ppm.

The plates are then incubated on a shaker at a temperature of 22 ⁰ C until a sufficient growth is observed in the untreated control. The evaluation is carried out photometrically at a wavelength of 620 nm. From the measured data of the various concentrations, the drug dose, which leads to a 50% inhibition of fungal growth compared to the untreated control (ED ₅₀ ), is calculated. literature

Cheng, F. and Oldfield, E. (2004): Inhibition of Isoprene Biosynthesis Pathway Enzymes by Phosphonates, Bisphosphonates, and Diphosphonates. J. Med. Chem. 47, 5149-5158.

Mayer, M.P., F.M. Hahn, D.J. Stillman & C.D. Poulter (1992): Disruption and mapping of IDI, the gene for the isopentenyl diphosphate isomerase in Saccharomyces cerevisiae. Yeast. 8, 743-748.

Ramos-Valdivia A., van der Heijden, R. and Verpoorte, R. (1997): isopentenyl diphosphate isomerase: a core enzyme in isoprenoid biosynthesis. A review of is biochemistry and function. NaL Prod. Rep. 14, 591-603.

Rohdich F., Bacher A. and Eisenreich W. (2004): Perspectives in anti-infective drug design. Bioorganic Chemistry 32, 292-308.

Street et al. (1994): Identification of Cysl39 and Glu207 as catalytically important groups in the active site of isopentenyl diphosphate: dimethylallyl diphosphate isomerase. Biochemistry 33, 4212-4217.

Thompson K., Dunford JE, Ebetino FH, Rogers MJ. (2002): Identification of a bisphosphonate that inhibits isopentenyl diphosphate isomerase and farnesyl diphosphate synthase. Biochemical and Bio ^' Physical Research Communications 290, 869-873.

Wouters J., Oudjama Y., Barkley SJ., Tricot C, Stalon V., Droogmans L., Poulter CD. (2003): Catalytic mechanism of Escherichia coli isopentenyl diphosphate isomerase involves Cys-67, Glu-116, and Tyr-104 as suggested by crystal structures of complexes with analogous and irreversible inhibitors. J. Biol. Chem. 278, 11903-1198.

Claims

claims

1. A method for identifying fungicides, characterized in that one

(a) a fungal polypeptide having the enzymatic activity of an IPP isomerase with a chemical compound or a mixture of chemical compounds under conditions which facilitate the interaction of the chemical compound with the

Allow polypeptide to contact,

(b) comparing the activity of IPP isomerase in the absence of a chemical compound with the activity of IPP isomerase in the presence of a chemical compound or a mixture of chemical compounds, and

(c) selecting the chemical compound that specifically inhibits the IPP isomerase.

2. The method according to claim 1, characterized in that one determines the activity of IPP isomerase by measuring the formation of phosphate from the product of the catalyzed by the IPP isomerase reaction.

3. The method according to claim 1 or 2, characterized in that one determines an inhibition of the enzymatic activity of the IPP isomerase in the presence of a chemical compound on the basis of a decreasing amount of phosphate.

4. The method according to claim 1 or 2, characterized in that one determines the reaction of IPP isomerase directly by means of a malachite green test.

5. The method according to any one of claims 1, characterized in that one tests in a further step (d) the fungicidal activity of the identified compound by bringing it into contact with a fungus.

6. The method according to any one of claims 1 to 6, characterized in that one uses an IPP isomerase from a phytopathogenic fungus.

7. Use of polypeptides having the activity of an IPP isomerase to identify fungicides.

8. Use of inhibitors of polypeptides having the activity of an IPP isomerase as fungicides.

9. A method for the control of phytopathogenic fungi, characterized in that one (a) a fungicidally active compound is identified in a method according to claim 1,

(b) formulating the identified compound appropriately, and

(c) brings into contact with the phytopathogenic fungus and / or its environment.

10. Use of fungicidal compounds, which are found in a process according to any one of claims 1 to 5, for the manufacture of fungicidal agents.

Nucleic acid according to claim 10, characterized in that it comprises a sequence selected from:

(a) a sequence according to SEQ ID NO: 1,

(b) sequences encoding a polypeptide comprising the amino acid sequence of SEQ ID NO: 2,

(c) sequences which hybridize to the sequences defined under a) at a hybridization temperature of 42-65 ° C, and

(d) sequences which have at least 80%, preferably at least 85% and more preferably at least -90% identity with the sequences defined under a) and b).

12. A DNA construct comprising a nucleic acid according to claim 10 or 11 and a heterologous promoter.

13. A vector comprising a nucleic acid according to claim 11 or 12, or a DNA construct according to claim 12.

14. A vector according to claim 14, characterized in that the nucleic acid is functionally linked to regulatory sequences which ensure the expression of the nucleic acid in pro- or eukaryotic cells.

15. A host cell containing a nucleic acid according to claim 11 or 12, a DNA construct according to claim 13 or a vector according to claim 14 or 15.

16. polypeptide having the biological activity of an IPP isomerase, which is encoded by a nucleic acid according to claim 11 or 12.

17. polypeptide having the biological activity of an IPP isomerase, which comprises an amino acid sequence according to SEQ ID NO: 2.