EP0956345A1 - Laccases mutantes - Google Patents

Laccases mutantes

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Publication number
EP0956345A1
EP0956345A1 EP97949990A EP97949990A EP0956345A1 EP 0956345 A1 EP0956345 A1 EP 0956345A1 EP 97949990 A EP97949990 A EP 97949990A EP 97949990 A EP97949990 A EP 97949990A EP 0956345 A1 EP0956345 A1 EP 0956345A1
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EP
European Patent Office
Prior art keywords
atom
laccase
leu
asn
val
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Application number
EP97949990A
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German (de)
English (en)
Inventor
Anders Hjelholt Pedersen
Allan Svendsen
Palle Schneider
Grethe Rasmussen
Joel R. Cherry
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Novozymes AS
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Novo Nordisk AS
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Publication of EP0956345A1 publication Critical patent/EP0956345A1/fr
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    • C—CHEMISTRY; METALLURGY
    • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
    • C12N—MICROORGANISMS OR ENZYMES; COMPOSITIONS THEREOF; PROPAGATING, PRESERVING, OR MAINTAINING MICROORGANISMS; MUTATION OR GENETIC ENGINEERING; CULTURE MEDIA
    • C12N9/00—Enzymes; Proenzymes; Compositions thereof; Processes for preparing, activating, inhibiting, separating or purifying enzymes
    • C12N9/0004—Oxidoreductases (1.)
    • C12N9/0055—Oxidoreductases (1.) acting on diphenols and related substances as donors (1.10)
    • C12N9/0057—Oxidoreductases (1.) acting on diphenols and related substances as donors (1.10) with oxygen as acceptor (1.10.3)
    • C12N9/0061—Laccase (1.10.3.2)

Definitions

  • the present invention relates to a method of designing laccase mutants with improved stability properties, which method is based on the hitherto unknown three-dimensional structure of laccases .
  • Laccase is a polyphenol oxidase (EC 1.10.3.2) which catalyses the oxidation of a variety of inorganic and aromatic compounds, particularly phenols, with the concomitant reduction of molecular oxygen to water.
  • Laccase belongs to a family of blue copper-containing oxidases which includes ascorbate oxidase and the mammalian plasma protein ceruloplasmin. All these enzymes are multi-copper- containing proteins. Because laccases are able to catalyze the oxidation of a variety of inorganic and aromatic compounds, laccases have been suggested in many potential industrial applications such as lignin modification, paper strengthening, dye transfer inhibition in detergents, phenol polymerization, hair colouring, and waste water treatment. A major problem with the use of laccases are their poor storage stability at temperatures above room temperature, especially at 40°C.
  • Example 1 of the present application we have tested the stability of various laccases at 40°C, and it can be seen that after 2 weeks of storage the laccase activity is down to less than 50% of the initial value, and at low pH the laccase activity after 2 weeks is zero. For many purposes such a decrease is unacceptable, so it is the purpose of the present invention to create laccase variants with improved stability by using the information of a three-dimensional structure of a Coprinus cinereus laccase. No three-dimensional structural information has been available for a laccase before. BRIEF DISCLOSURE OF THE INVENTION
  • the invention relates to a method of constructing a variant of a parent Coprinus laccase, which variant has laccase activity and improved stability as compared to said parent laccase, which method comprises
  • Coprinus laccase variant which as compared to the parent Coprinus laccase, has been modified in the amino acid residue or structural part identified in i) so as to alter the stability, and, optionally,
  • the present invention relates to a method of constructing a variant of a parent Coprinus-like laccase, which variant has laccase activity and improved stability as compared to said parent laccase, which method comprises i) comparing the three-dimensional amino acid structure of the Coprinus laccase with an amino acid sequence of a Coprinus-like laccase,
  • the invention relates to variants of a Coprinus laccase and of Coprinus-like laccases, DNA encoding such variants and methods of preparing the variants. Finally, the invention relates to the use of the variants for various industrial purposes .
  • Polyporus pinsi tus (I) laccase comprising the amino acid sequence shown in SEQ ID No. 2: 74.4%;
  • Polyporus pinsi tus (II) laccase comprising the amino acid sequence shown in SEQ ID No. 3: 73.8%;
  • Phlebia radiata laccase comprising the amino acid sequence shown 5 in SEQ ID No. 4: 69.9% ;
  • Rhizoctonia solani (I) laccase comprising the amino acid sequence shown in SEQ ID No. 5: 64.8%;
  • Rhizoctonia solani (II) laccase comprising the amino acid sequence shown in SEQ ID No. 6: 63.0%; 10 Rhizoctonia solani (III) laccase comprising the amino acid sequence shown in SEQ ID No. 7: 61.0%;
  • Rhizoctonia solani (IV) laccase comprising the amino acid sequence shown in SEQ ID No . 8: 59.7%;
  • Myceliophthora thermophila laccase comprising the amino acid sequence shown in SEQ ID No . 10: 56.5%.
  • laccases they are considered to belong to the same class of laccases, namely the class of " Coprinus-like laccases".
  • Coprinus-like laccase is intended to indicate a laccase which, on the amino acid level, displays a homology of at least 50% and less than
  • derived from is intended not only to indicate a laccase produced or producible by a strain of the organism in question, but also a laccase encoded by a DNA sequence isolated from such strain and produced in a host organism containing said DNA sequence.
  • the term is intended to indicate a laccase which is encoded by a DNA sequence of synthetic and/or cDNA origin and which has the identifying characteristics of the laccase in question.
  • the Coprinus laccase which was used to elucidate the three- dimensional structure forming the basis for the present invention consists of the 539 amino acids derived from Coprinus cinereus laccase IFO 8371 as disclosed in sequence ID No . 1.
  • the obtained three-dimensional structure is believed to be representative for the structure of any Coprinus-like laccase.
  • the structure of the laccase was solved in accordance with the principle for X-ray crystallographic methods given in "X-Ray Structure Determination", Stout, G.K. and Jensen, L.H., John Wiley & Sons, inc. NY, 1989.
  • the structural coordinates for the solved crystal structure of the laccase at 2.2 A resolution using the isomorphous replacement method are given in a standard PDB format (Brookhaven Protein Data Base) in Appendix 1. It is to be understood that Appendix 1 forms part of the present application.
  • the amino acid residues of the enzyme are identified by three-letter amino acid code (capitalized letters) .
  • the laccase structure is made up of three plastocyanin-like domains . These three domains all have a similar beta-barrel fold. 3 copper atoms were observed in the three-dimensional structure :
  • type 1 copper ion is coordinated by two histidines and one cysteine.
  • type 2 copper of the trinuclear centre is missing in the structure disclosed in the present application.
  • type 3 copper consists of two type 3 copper atoms (pair of copper atoms) bound to a total of 6 histidine ligands .
  • Q243 in sequence ID No. 1 is an E225 in the crystallized protein.
  • Coprinus laccase structure may be identified in other Coprinus- like laccases on the basis of a model (or solved) structure of the relevant Coprinus-like laccase or simply on the basis of an alignment between the amino acid sequence of the Coprinus-like laccase in question with that of the Coprinus laccase used herein for identifying the amino acid residues of the respective structural elements.
  • Coprinus laccase variants of the invention which are defined by modification of specific amino acid residues of the parent Coprinus laccase, it will be understood that variants of Coprinus-like laccases modified in an equivalent position (as determined from the best possible amino acid sequence alignment between the respective sequences) are intended to be covered as well.
  • step i) of the methods of the invention may be performed by use of any suitable computer programme capable of analysing and/or comparing amino acid sequences .
  • the structural part which is identified in step i) of the methods of the invention may be composed of one amino acid residue. However, normally the structural part comprises more than one amino acid residue, typically constituting one of the above mentioned parts of the Coprinus structure such as one of the copper centres .
  • useful laccase variants may be modified in one or more amino acid residues present within 15 A from any copper ion, preferably variants which are modified within 10 A from any copper ion, in particular variants which are modified within 5 A from any copper ion.
  • BIOSYM technologies The spatial coordinates are presented showing the bonds between the atoms .
  • the copper atoms are presented as well as the water atoms.
  • the program package contains a part which can be used for creating subsets. This part is used for creating a 5A, 10A and 15A subset around all Cu-ions present in the structure (the command ZONE is used) .
  • the found subsets contain all residues having an atom within 5, 10 and 15A from any of the Cu-ions present in the structure. All residues having an atom within this subset are compiled and written out by the LIST MOLECULE command.
  • amino acid residues found in this way within a distance of 15 A from a copper ion in the Coprinus cinereus laccase are the following (SEQ ID No 1 numbering) : M27, V46, G51, P52, 154, L64, L76, T79, S80, 181, H82, W83,H84, G85, L86, F87, Q88, R89, T91, N92, W93, A94, D95, G96, A97, D98, G99, V100, N101, Q102, C103, P104, Y113, F115, H120, G122, T123, F124, W125, Y126, H127, S128, H129, F130, G131, T132, Q133, Y134, C135, D136, G137, L138, R139, G140, P141, M142, V143, 1144, 1164, T165, L166, A167, D168, H170, G179, A180, A181, Q182, P
  • amino acid residues found within a distance of 10 A from a copper ion in the Coprinus cinereus laccase are the following:
  • amino acid residues found within a distance of 5 A from a copper ion in the Coprinus cinereus laccase are the following:
  • the 15A/10A/5A regions can be found in other laccases by comparison of the modelled structures or by taking the sequence homology numbers .
  • the modification of an amino acid residue or structural part is typically accomplished by suitable modifications of a DNA sequence encoding the parent enzyme in question.
  • modified as used in the methods according to the invention is intended to have the following meaning: When used in relation to an amino acid residue the term is intended to mean replacement of the amino acid residue in question with another amino acid residue. When used in relation to a structural part, the term is intended to mean: replacement of one or more amino acid residues of said structural part with other amino acid residues, or addition of one or more amino acid residues to said part, or deletion of one or more amino acid residues of said structural part .
  • the construction of the variant of interest is accomplished by cultivating a microorganism comprising a DNA sequence encoding the variant under conditions which are conducive for producing the variant, and optionally subsequently recovering the variant from the resulting culture broth. This is described in detail further below.
  • CcL Coprinus cinereus laccase comprising the amino acid sequence shown in SEQ ID No. 1
  • PpLl Polyporus pinsi tus (I) laccase comprising the amino acid sequence shown in SEQ ID No . 2 ;
  • PpL2 Polyporus pinsi tus (II) laccase comprising the amino acid sequence shown in SEQ ID No . 3 ;
  • PrL Phlebia radiata laccase comprising the amino acid sequence shown in SEQ ID No. 4 ;
  • Rhizoctonia solani (I) laccase comprising the amino acid sequence shown in SEQ ID No . 5 ;
  • StL Scytalidium thermophilum laccase comprising the amino acid sequence shown in SEQ ID No . 9 ;
  • MtL Myceliophthora thermophila laccase comprising the amino acid sequence shown in SEQ ID No. 10.
  • a variant of a parent Coprinus laccase which comprises one or more of the following substitutions in SEQ ID No. 1:
  • a variant of a parent Polyporus pinsi tus (I) laccase which comprises a mutation in a position corresponding to at least one of the following positions in SEQ ID No. 2: W107 A, V, L, I, P, F, M, G, S, T, C, Y, N, Q, D, E, K, R, H;
  • a variant of a parent Polyporus pinsi tus (II) laccase which comprises a mutation in a position corresponding to at least one of the following positions in SEQ ID No. 3: W107 A, V, L, I, P, F, M, G, S, T, C, Y, N, Q, D, E, K, R, H; Y116 A, V, L, I, P, F, W, G, S, T, C, M, N, Q, D, E, K, R, H; Y108 A, V, L, I, P, F, W, G, S, T, C, M, N, Q, D, E, K, R, H; Y152 A, V, L , I , P , F , W, G , S , T , C , M, N, Q , D , E , K, R, H ; M57 A, V, L , I , P , F , W, G , S , T ,
  • a variant of a parent Phlebia radiata laccase, which comprises a mutation in a position corresponding to at least one of the following positions in SEQ ID No. 4:
  • a variant of a parent Phlebia radiata laccase, which comprises a mutation in a position corresponding to at least one of the following positions in SEQ ID No. 4: W128 F, H;
  • Rhizoctonia solani (I) laccase which comprises a mutation in a position corresponding to at least one of the following positions in SEQ ID No . 5:
  • Rhizoctonia solani (I) laccase which comprises a mutation in a position corresponding to at least one of the following positions in SEQ ID No. 5:
  • Rhizoctonia solani (II) laccase which comprises a mutation in a position corresponding to at least one of the following positions in SEQ ID No . 6: W439 A, V, L, I, P, F, M, G, S, T, C, Y, N, Q, D, E, K, R, H;
  • Rhizoctonia solani (II) laccase which comprises a mutation in a position corresponding to at least one of the following positions in SEQ ID No. 6: W439 F, H; W125 F, H; Y134 F; Y126 F; Y170 F; M75 F, V, I, L, Q.
  • a variant of a parent Rhizoctonia solani (III) laccase which comprises a mutation in a position corresponding to at least one of the following positions in SEQ ID No. 7: W411 A, V, L, I, P, F, M, G, S, T, C, Y, N, Q, D, E, K, R, H; W125 A, V, L, I, P, F, M, G, S, T, C, Y, N, Q, D, E, K, R, H; Y134 A, V, L, I, P, F, W, G, S, T, C, M, N, Q, D, E, K, R, Hj Y126 A, V, L, I, P, F, W, G, S, T, C, M, N, Q, D, E, K, R, H; Y170 A, V, L, I, P, F, W, G, S, T, C, M, N, Q, D, E, K, R, H; Y
  • Rhizoctonia solani (III) laccase which comprises a mutation in a position corresponding to at least one of the following positions in SEQ ID No. 7:
  • a variant of a parent Rhizoctonia solani (IV) laccase which comprises a mutation in a position corresponding to at least one of the following positions in SEQ ID No . 8:
  • Rhizoctonia solani (IV) laccase which comprises a mutation in a position corresponding to at least one of the following positions in SEQ ID No. 8:
  • a variant of a parent Scytalidium thermophilum laccase which comprises a mutation in a position corresponding to at least one of the following positions in SEQ ID No. 9: M483 A, V, L, I, P, F, W, G, S, T, C, Y, N, Q, D, E, K, R, H
  • a variant of a parent Myceliophthora thermophila laccase which comprises a mutation in a position corresponding to at least one of the following positions in SEQ ID No. 10:
  • a variant of a parent Myceliophthora thermophila laccase which comprises a mutation in a position corresponding to at least one of the following positions in SEQ
  • the DNA sequence encoding a parent laccase may be isolated from any cell or microorganism producing the laccase in question, using various methods well known in the art.
  • a genomic DNA and/or cDNA library should be constructed using chromosomal DNA or messenger RNA from the organism that produces the laccase to be studied.
  • homologous, labelled oligonucleotide probes may be synthesized and used to identify laccase-encoding clones from a genomic library prepared from the organism in question.
  • a labelled oligonucleotide probe containing sequences homologous to a known laccase gene could be used as a probe to identify laccase-encoding clones, using hybridization and washing conditions of lower stringency.
  • a method for identifying laccase-encoding clones involves inserting cDNA into an expression vector, such as a plasmid, transforming laccase-negative fungi with the resulting cDNA library, and then plating the transformed fungi onto agar containing a substrate for laccase, thereby allowing clones expressing the laccase to be identified.
  • an expression vector such as a plasmid, transforming laccase-negative fungi with the resulting cDNA library
  • the DNA sequence encoding the enzyme may be prepared synthetically by established standard methods, e.g. the phosphoroamidite method.
  • oligonu- cleotides are synthesized, e.g. in an automatic DNA synthesizer, purified, annealed, ligated and cloned in appropriate vectors.
  • the DNA sequence may be of mixed genomic and synthetic origin, mixed synthetic and cDNA origin or mixed genomic and cDNA origin, prepared by ligating fragments of synthetic, genomic or cDNA origin (as appropriate, the fragments corresponding to various parts of the entire DNA sequence) , in accordance with standard techniques.
  • the DNA sequence may also be prepared by polymerase chain reaction (PCR) using specific primers.
  • mutations may be introduced using synthetic oligonucleotides . These oligonucleotides contain nucleotide sequences flanking the desired mutation sites; mutant nucleotides are inserted during oligonucleotide synthesis.
  • a single-stranded gap of DNA, bridging the laccase-encoding sequence is created in a vector carrying the laccase gene.
  • the synthetic nucleotide, bearing the desired mutation is annealed to a homologous portion of the single- stranded DNA. The remaining gap is then filled in with T7 DNA polymerase and the construct is ligated using T4 ligase.
  • the random mutagenesis of a DNA sequence encoding a parent laccase may conveniently be performed by use of any method known in the art .
  • the random mutagenesis may be performed by use of a suitable physical or chemical mutagenizing agent, by use of a suitable oligonucleotide, or by subjecting the DNA sequence to PCR generated mutagenesis.
  • the random mutagenesis may be performed by use of any combination of these mutagenizing agents .
  • the mutagenizing agent may, e.g., be one which induces transitions, transversions, inversions, scrambling, deletions, and/or insertions .
  • Examples of a physical or chemical mutagenizing agent suitable for the present purpose include ultraviolet (UV) irradiation, hydroxylamine, N-methyl-N' -nitro-N-nitrosoguanidine (MNNG) , O-methyl hydroxylamine, nitrous acid, ethyl methane sulphonate (EMS) , sodium bisulphite, formic acid, and nucleotide analogues .
  • UV ultraviolet
  • MNNG N-methyl-N' -nitro-N-nitrosoguanidine
  • EMS ethyl methane sulphonate
  • sodium bisulphite formic acid
  • nucleotide analogues examples include ultraviolet (UV) irradiation, hydroxylamine, N-methyl-N' -nitro-N-nitrosoguanidine (MNNG) , O-methyl hydroxylamine, nitrous acid, ethyl methane sulphonate (EMS) , sodium bisulphite,
  • the mutagenesis is typically performed by incubating the DNA sequence encoding the parent enzyme to be mutagenized in the presence of the mutagenizing agent of choice under suitable conditions for the mutagenesis to take place, and selecting for mutated DNA having the desired properties .
  • the oligonucleotide may be doped or spiked with the three non-parent nucleotides during the synthesis of the oligonucleotide at the positions which are to be changed.
  • the doping or spiking may be done so that codons for unwanted amino acids are avoided.
  • the doped or spiked oligonucleotide can be incorporated into the DNA encoding the laccase enzyme by any published technique, using e.g. PCR, LCR or any DNA polymerase and ligase.
  • PCR-generated mutagenesis When PCR-generated mutagenesis is used, either a chemically treated or non-treated gene encoding a parent laccase enzyme is subjected to PCR under conditions that increase the mis- incorporation of nucleotides (Deshler 1992; Leung et al . , Technique, Vol.l, 1989, pp. 11-15) .
  • a mutator strain of E. coli (Fowler et al . , Molec . Gen. Genet., 133, 1974, pp. 179-191), S . cereviseae or any other microbial organism may be used for the random mutagenesis of the DNA encoding the laccase enzyme by e.g. transforming a plasmid containing the parent enzyme into the mutator strain, growing the mutator strain with the plasmid and isolating the mutated plasmid from the mutator strain. The mutated plasmid may subsequently be transformed into the expression organism.
  • the DNA sequence to be mutagenized may conveniently be present in a genomic or cDNA library prepared from an organism expressing the parent laccase enzyme.
  • the DNA se- quence may be present on a suitable vector such as a plasmid or a bacteriophage, which as such may be incubated with or otherwise exposed to the mutagenizing agent.
  • the DNA to be mutagenized may also be present in a host cell either by being integrated in the genome of said cell or by being present on a vector harboured in the cell.
  • the DNA to be mutagenized may be in isolated form. It will be understood that the DNA sequence to be subjected to random mutagenesis is preferably a cDNA or a genomic DNA sequence .
  • telomere amplification may be performed in accordance with methods known in the art, the presently preferred method being PCR-generated amplification using oligonucleotide primers prepared on the basis of the DNA or amino acid sequence of the parent enzyme.
  • the mutated DNA is expressed by culturing a suitable host cell carrying the DNA sequence under conditions allowing expression to take place.
  • the host cell used for this purpose may be one which has been transformed with the mutated DNA sequence, optionally present on a vector, or one which was carried the DNA sequence encoding the parent enzyme during the mutagenesis treatment.
  • suitable host cells are fungal hosts such as Aspergillus niger or Aspergillus oryzae .
  • the mutated DNA sequence may further comprise a DNA sequence encoding functions permitting expression of the mutated DNA sequence .
  • the random mutagenesis may advantageously be localized to a part of the parent laccase in question. This may, e.g., be advantageous when certain regions of the enzyme have been identified to be of particular importance for a given property of the enzyme, and when modified are expected to result in a variant having improved properties. Such regions may normally be identified when the tertiary structure of the parent enzyme has been elucidated and related to the function of the enzyme.
  • the localized random mutagenesis is conveniently performed by use of PCR-generated mutagenesis techniques as described above or any other suitable technique known in the art .
  • the DNA sequence encoding the part of the DNA sequence to be modified may be isolated, e.g. by being inserted into a suitable vector, and said part may subsequently be subjected to mutagenesis by use of any of the mutagenesis methods discussed above.
  • a microorganism capable of expressing the mutated laccase enzyme of interest is incubated on a suitable medium and under suitable conditions for the enzyme to be secreted, the medium being provided with a double filter comprising a first protein- binding filter and on top of that a second filter exhibiting a low protein binding capability.
  • the microorganism is located on the second filter.
  • the first filter comprising enzymes secreted from the microorganisms is separated from the second filter comprising the microorganisms.
  • the first filter is subjected to screening for the desired enzymatic activity and the corresponding microbial colonies present on the second filter are identified.
  • the filter used for binding the enzymatic activity may be any protein binding filter e.g. nylon or nitrocellulose.
  • the top filter carrying the colonies of the expression organism may be any filter that has no or low affinity for binding proteins e.g. cellulose acetate or DuraporeTM.
  • the filter may be pretreated with any of the conditions to be used for screening or may be treated during the detection of enzymatic activity.
  • the enzymatic activity may be detected by a dye, fluorescence, precipitation, pH indicator, IR-absorbance or any other known technique for detection of enzymatic activity.
  • the detecting compound may be immobilized by any immobilizing agent, e.g., agarose, agar, gelatine, polyacrylamide, starch, filter paper, cloth; or any combination of immobilizing agents.
  • immobilizing agent e.g., agarose, agar, gelatine, polyacrylamide, starch, filter paper, cloth; or any combination of immobilizing agents.
  • Coprinus variants or Coprinus-like variants should be investigated at 40 °C for 2 weeks at pH 5, 8 and 9.3, respectively.
  • the stability of the parent laccase and the variants may be tested both in a liquid buffer formulation and in a lyophilized form.
  • the residual activity of the variants following two weeks of incubation are then compared to the residual activity of the parent laccase, and variants with an improved stability at either pH 5, 8 or 9.3 are selected.
  • the laccase activity was measured using 10- (2-hydroxyethyl) -phenoxazine (HEPO) as substrate for the various laccases.
  • HEPO was synthesized using the same procedure as described for 10- (2-hydroxyethyl) - phenothiazine, (G. Cauquil in Bulletin de la Society Chemique de France, 1960, p. 1049).
  • oxygen laccases E.C. 1.10.3.2
  • the Coprinus cinereus laccase was measured using 0.4 mM HEPO in 50 mM sodium acetate, pH 5.0, 0.05% TWEEN-20 at 30°C. The absorbance at 528 nm was followed for 200 s and the rate calculated from the linear part of the progress curve.
  • the Myceliophthora thermophila laccase was measured using 0.4 mM HEPO in 25 mM Tris-HCl, pH 7.5, 0.05% Tween-20 at 30 °C. The absorbance at 528 nm was followed for 200 s and the rate calculated from the linear part of the progress curve.
  • the Polyporus pinsi tus laccase was measured using 0.4 mM HEPO in 50 mM MES-NaOH, pH 5.5. The absorbance at 528 nm was followed for 200 s and the rate calculated from the linear part of the progress curve.
  • a DNA sequence encoding the variant produced by methods described above, or by any alternative methods known in the art can be expressed, in enzyme form, using an expression vector which typically includes control sequences encoding a promoter, operator, ribosome binding site, translation initiation signal, and, optionally, a repressor gene or various activator genes.
  • the recombinant expression vector carrying the DNA sequence encoding a laccase variant of the invention may be any vector which may conveniently be subjected to recombinant DNA procedures, and the choice of vector will often depend on the host cell into which it is to be introduced.
  • the vector may be an autonomously replicating vector, i.e. a vector which exists as an extrachromosomal entity, the replication of which is independent of chromosomal replication, e.g. a plasmid, a bacteriophage or an extrachromosomal element, minichromosome or an artificial chromosome.
  • the vector may be one which, when introduced into a host cell, is integrated into the host cell genome and replicated together with the chromosome (s) into which it has been integrated.
  • the DNA sequence should be operably connected to a suitable promoter sequence .
  • the promoter may be any DNA sequence which shows transcriptional activity in the host cell of choice and may be derived from genes encoding proteins either homologous or heterologous to the host cell .
  • suitable promoters for directing the transcription of the DNA sequence encoding a laccase variant of the invention, especially in a fungal host are those derived from the gene encoding A . oryzae TAKA amylase, Rhizomucor miehei aspartic proteinase, A . niger neutral ⁇ -amylase, A . niger acid stable ⁇ -amylase, A .
  • the expression vector of the invention may also comprise a suitable transcription terminator and, in eukaryotes, poly- adenylation sequences operably connected to the DNA sequence encoding the laccase variant of the invention. Termination and polyadenylation sequences may suitably be derived from the same sources as the promoter.
  • the vector may further comprise a DNA sequence enabling the vector to replicate in the host cell in question.
  • a DNA sequence enabling the vector to replicate in the host cell in question. Examples of such sequences are the origins of replication of plasmids pUC19, pACYC177, pUBllO, pE194, pAMBl and pIJ702.
  • the vector may also comprise a selectable marker, e.g. a gene, the product of which complements a defect in the host cell, such as one which confers antibiotic resistance such as ampicillin, kanamycin, chloramphenicol or tetracyclin resistance.
  • the vector may comprise Aspergillus selection markers such as amdS, argB, niaD and sC, a marker giving rise to hygromycin resistance, or the selection may be accomplished by co-transformation, e.g. as described in WO 91/17243.
  • Aspergillus selection markers such as amdS, argB, niaD and sC, a marker giving rise to hygromycin resistance, or the selection may be accomplished by co-transformation, e.g. as described in WO 91/17243.
  • the cell of the invention is advantageously used as a host cell in the recombinant production of a laccase variant of the invention.
  • the cell may be transformed with the DNA construct of the invention encoding the variant, conveniently by integrating the DNA construct (in one or more copies) in the host chromosome. This integration is generally considered to be an advantage as the DNA sequence is more likely to be stably maintained in the cell. Integration of the DNA constructs into the host chromosome may be performed according to conventional methods, e.g. by homologous or heterologous recombination. Alternatively, the cell may be transformed with an expression vector as described above in connection with the different types of host cells.
  • the cell of the invention may be a cell of a higher organism such as a mammal or an insect, but is preferably a microbial cell, e.g. a fungal cell.
  • the filamentous fungus may advantageously belong to a species of Aspergillus, e.g. Aspergillus oryzae or Aspergillus niger.
  • Fungal cells may be transformed by a process involving protoplast formation and transformation of the protoplasts followed by regeneration of the cell wall in a manner known per se .
  • a suitable procedure for transformation of Aspergillus host cells is described in EP 238 023.
  • the present invention relates to a method of producing a laccase variant of the invention, which method comprises cultivating a host cell as described above under conditions conducive to the production of the variant and recovering the variant from the cells and/or culture medium.
  • the medium used to cultivate the cells may be any conventional medium suitable for growing the host cell in question and obtaining expression of the laccase variant of the invention. Suitable media are available from commercial suppliers or may be prepared according to published recipes (e.g. as described in catalogues of the American Type Culture Collection) .
  • the laccase variant secreted from the host cells may conveniently be recovered from the culture medium by well-known procedures, including separating the cells from the medium by centrifugation or filtration, and precipitating proteinaceous components of the medium by means of a salt such as ammonium sulphate, followed by the use of chromatographic procedures such as ion exchange chromatography, affinity chromatography, or the like.
  • the laccase variants of this invention possesses valuable properties allowing for various industrial applications, in particular lignin modification, paper strengthening, dye transfer inhibition in detergents, phenol polymerization, hair dyeing, bleaching of textiles (in particular bleaching of denim as described in WO 96/12845 and WO 96/12846) and waste water treatment .
  • Any detergent composition normally used for enzymes may be used, e.g., the detergent compositions disclosed in WO 95/01426.
  • the storage stability of the Myceliophthora thermophila and the Polyporus pinsi tus laccases was tested for 2 weeks at 40°C at pH 5, 8 and 9.3, respectively.
  • the laccase (1 mg/ l) was dialyzed against 0.1 M sodium acetate, pH 5, or 0.1 M Tris-maleate, pH 8, or 0.1 M Tris- maleate, pH 9.3. Following dialysis the different preparations were poured into two sets of glass vials with screw caps: one for the liquid formulation and the other one for the lyophilized form. After two weeks of incubation the enzyme activity was measured as described above and the residual activity of the enzymes was calculated in percentage using a preparation of Myceliophthora thermophila and Polyporus pinsi tus kept at 4°C as references. The results are given below in Table 1 and 2.
  • Coprinus cinereus CcL
  • other sequences e.g., Polyporus pinsi tus
  • Coprinus-like 3 D-structures can be found.
  • Polyporus pinsi tus differs in a number of residues.
  • the model may be built using the HOMOLOGY program from BIOSYM.
  • the program substitutes the amino acids in the Coprinus cinereus with amino acids from Polyporus pinsi tus in the homologous positions defined in the program as structurally conserved regions (SCR) .
  • SCR structurally conserved regions
  • the residues in between are built using the LOOP option with GENERATE. Using these steps a crude model may be obtained which gives information of spatial interactions.
  • the structure can be refined using the method described in the HOMOLOGY package.
  • Myceliophthora thermophila laccase variants were measured using 0.4 mM HEPO in 0.1 M Tris-maleate, pH 7.5, 0.05% TWEEN-20 at 30°C. The absorbance at 528 nm was followed for 200 s and the rate calculated from the linear part of the progress curve.
  • the storage stability of the Myceliophthora thermophila variants were tested for 4 weeks at 40°C at pH 5, 7, and 9.3, respectively.
  • the laccase (1 mg/ml) was dialyzed against 0.1 M Tris-maleate, pH 5 or 0.1 M Tris-maleate, pH 7 or 0.1 M Tris- maleate, pH 9.3.
  • the different preparations were poured into two set of glass vials with screw caps: one for the liquid formulation and the other set of glasses for lyophilization.
  • the enzyme activity was measured as described above and the residual activity of the variants were calculated in percentage using a preparation kept at 4°C as reference.
  • Residual Residual Residual activi ty pH 5 activity, activity, pH 7 pH 9.2
  • W136F has increased stability in both formulations.
  • ATOM 104 CB ASN A 15 0 2.114 35.721 -0.875 1.00 21.13
  • ATOM 205 CB ASN A 29 0 15.982 42.446 4.764 1.00 21.06
  • ATOM 206 CG ASN A 29 0 16.475 43.654 5.522 1.00 22.44
  • ATOM 286 CA ASN A 41 0 30.536 44.171 22.840 1.00 25.14 ATOM 287 C
  • ATOM 302 CA ASN A 43 0 27.316 48.660 19.255 1.00 26.50
  • ATOM 400 CA PRO A 55 0 -4.286 46.589 6.014 1.00 26.57
  • ATOM 401 C PRO A 55 0 -4.909 45.414 6.723 1.00 27.10
  • ATOM 407 CA THR A 56 0 -5.214 43.024 7.065 1.00 25.52
  • ATOM 413 N MET A 57 0 -3.317 43.311 8.558 1.00 26.01
  • ATOM 414 CA MET A 57 0 -2.553 43.099 9.801 1.00 26.57
  • ATOM 441 CA PRO A 60 0 2.460 50.669 12.916 1.00 26.19
  • ATOM 442 C PRO A 60 0 3.312 49.591 13.595 1.00 25.29
  • ATOM 469 CA HIS A 64 0 11.478 44.539 21.261 1.00 15.51
  • ATOM 623 CB ASN A 83 0 10.249 51.747 25.937 1.00 15.23 ATOM 624 CG ASN A 83 0 10.112 50.745 27.063 1.00 16.00
  • ATOM 815 CA TYR A 108 0 13.498 40.148 18.302 1.00 12.19
  • ATOM 841 OG SER A 110 0 5.212 44.481 16.508 1.00 15.32 ATOM 842 N HIS A 111 0 6.396 44.395 19.359 1.00 14.60
  • ATOM 864 CA GLY A 113 0 -0.554 44.236 19.433 1.00 19.69
  • ATOM 880 CD GLN A 115 0 3.558 45.024 13.418 1.00 17.73
  • ATOM 910 CA GLY A 119 0 5.671 36.889 11.313 1.00 19.00

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Abstract

L'invention concerne un procédé pour produire des formes mutantes de laccase qui présentent des propriétés de stabilité améliorées. Le procédé est basé sur une structure tridimensionnelle, inconnue jusqu'ici, de laccase Coprinus cinereus.
EP97949990A 1996-12-19 1997-12-16 Laccases mutantes Withdrawn EP0956345A1 (fr)

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WO2000037654A2 (fr) 1998-12-23 2000-06-29 Genencor International, Inc. Enzymes d'oxydation du phenol
US6329332B1 (en) * 1998-12-23 2001-12-11 Genencor International, Inc. Pleurotus phenol oxidizing enzymes
US6322596B1 (en) 1999-01-26 2001-11-27 Kimberly-Clark Worldwide, Inc. Method of decolorizing a dyed material in a predetermined pattern
AU2001254620A1 (en) * 2000-04-28 2001-11-12 Novozymes A/S Lipolytic enzyme variant
US7319112B2 (en) 2000-07-14 2008-01-15 The Procter & Gamble Co. Non-halogenated antibacterial agents and processes for making same
US6905853B1 (en) 2000-09-07 2005-06-14 Genencor International, Inc. Phenol oxidizing enzyme variants
CA2502304C (fr) 2002-10-08 2013-10-01 Genencor International, Inc. Peptides de liaison phenoliques
US10781428B2 (en) 2014-12-02 2020-09-22 Novozymes A/S Laccase variants and polynucleotides encoding same

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US5480801A (en) * 1993-09-17 1996-01-02 Novo Nordisk A/S Purified PH neutral Rhizoctonia laccases and nucleic acids encoding same
WO1995033836A1 (fr) * 1994-06-03 1995-12-14 Novo Nordisk Biotech, Inc. Phosphonyldipeptides efficaces dans le traitement de maladies cardiovasculaires
WO1995033837A1 (fr) * 1994-06-03 1995-12-14 Novo Nordisk Biotech, Inc. Laccases purifiees de scytalidium et acides nucleiques les codant
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WO1996006930A1 (fr) * 1994-08-26 1996-03-07 Novo Nordisk A/S Laccases obtenues a partir de coprinaceae
AU4483496A (en) * 1995-02-03 1996-08-21 Novo Nordisk A/S A method of designing alpha-amylase mutants with predetermined properties

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