US20090075328A1

US20090075328A1 - Process for the overexpression of dehydrogenases

Info

Publication number: US20090075328A1
Application number: US12/168,227
Authority: US
Inventors: Tilman Spellig
Original assignee: Individual
Current assignee: Individual
Priority date: 2002-02-01
Filing date: 2008-07-07
Publication date: 2009-03-19
Also published as: US20040091987A1; US7416866B2

Abstract

A process for the overexpression of dehydrogenases, especially for the overexpression of Δ¹-dehydrogenases, in particular for the overexpression of 3-keto steroid-Δ¹-dehydrogenases, as well as for the bacteria, plasmids and DNA sequences that can be used for the overexpression, is described.

Description

This invention relates to a process for the overexpression of dehydrogenases, especially Δ¹-dehydrogenases, in particular 3-keto steroid-Δ¹-dehydrogenases as well as the bacteria, plasmids and DNA sequences that are used for the overexpression.
The 3-keto steroid-Δ¹-dehydrogenase is an enzyme that fulfills an important function in steroid metabolism. With the aid of this enzyme, the selective introduction of a double bond at 1-position in the steroid skeleton is made possible. This reaction is of great importance for the synthesis of a wide variety of pharmaceutical active ingredients [e.g., betamethasone, deflazacort, fluocortolone, hydroxy acid, prednisolone, etc.]. It would be desirable to make available large amounts of this enzyme for a microbiological reaction.
For processes for microbial materials conversion, such as, e.g., steroid transformations, wild strains of yeasts, fungi and bacteria are generally used [see, i.a., Kieslich, K. (1980), Steroid Conversions, In: Economic Microbiology—Microbial Enzymes and Transformation, Rose, A. H. (ed.), Academic Press, London, Vol. V, pp. 370-453; Kieslich, K. and Sebek, O. K. (1980) Microbal Transformations of Steroids, In: Annual Reports on Fermentation Processes, Perlman, D. (ed.), Academic Press, New York, Vol. 3, pp. 275-304; Kieslich, K. (ed.) (1984) Biotransformation, Biotechnology, Vol. 6a, Rehm, H. J. and Reed, G. (eds.), Verlag Chemie, Weinheim]. In isolated cases, mutants that are also derived from wild strains and that are obtained by standard mutagenesis and selection processes are used [see, i.a., U.S. Pat. No. 3,102,080; Seidel, L. and Hörhold, C. (1992) J Basic Microbiol 32:49-55; EP 0322081 B1; U.S. Pat. No. 5,298,398]. Thus, e.g., in biotechnological processes for selective dehydrogenation, the endogenic catalytic activity of different microorganisms, i.a., Arthrobacter simplex and Bacillus sphaericus, is used [Sedlaczek (1988) Crit Rev Biotechnol. 7:187-236; U.S. Pat. No. 2,837,464; U.S. Pat. No. 3,010,876; U.S. Pat. No. 3,102,080].
It is also known that Δ¹-dehydrogenase genes of Arthrobacter simplex [Choi, K. P. et al. (1995) J Biochem 117:1043-1049; Molnar, I. et al. (1995) Mol Microbiol 15:895-905], Comamonas testosteroni [Plesiat, P. et al. (1991) J Bacteriol 173:7219-7227] and Nocardia opaca [Drobnic, K. et al. (1993) Biochem Biophys Res Com 190:509-515; SUISS-PROT AC: Q04616] were cloned, sequenced and functionally characterized. Also, DNA sequences were published from Mycobacterium tuberculosis and Rhodococcus rhodochrous, and because of their similarity to the above-mentioned Δ¹-dehydrogenase genes, said sequences can be considered as presumable dehydrogenase genes [http://www.sanger.ac.uk/Projects/M_tuberculosis; GenBank AC: 007847].
Limitation of the known biotransformation processes lies in the fact that the latter are in general process optimizations that are concentrated predominantly in the improvement of reaction conditions and process parameters, such as, e.g., type and composition of nutrients, execution of the process, substrate administration, etc. In particular, the processes for selective dehydrogenation have a number of drawbacks, such as, e.g., i) complete reaction of the educt only at very low substrate concentrations [U.S. Pat. No. 3,102,080], ii) long operating times, and iii) the formation of secondary zones—such as, e.g., 11α-hydroxyandrosta-1,4-diene-3,17-dione in the reaction of hydrocortisone to form prednisolone, which must be separated by expensive purification processes. These drawbacks result in the fact that the production process is very expensive.
It has now been found that by directed alteration of the microorganisms that catalyze the materials conversion with molecular-biological methods, better, more efficient and purposeful biotransformations of steroid molecules can be achieved. The biotransformation reactions are performed with bacteria that contain plasmids for overexpression of 3-keto steroid-Δ¹-dehydrogenase genes.
The bacteria that are used include in particular representatives of the gram-positive genus Bacillus, such as Bacillus subtilis, Bacillus sphaericus, Bacillus lichen form is, Bacillus lentus and Bacillus megaterium, but also gram-negative representatives, such as Escherichia coli and Pseudomonas species.
By directed strain development with molecular-biological methods, microorganisms are designed that accelerate and simplify the syntheses of active ingredients, by i) the use of very high substrate concentrations with ii) unaltered operating times being possible, without iii) disruptive secondary zones being developed.
In particular, selective dehydrogenation at 1-position of the steroid skeleton is described here, whereby 3-keto steroid-Δ¹-dehydrogenase genes that are isolated from microorganisms are used.
According to the invention, a process for selective introduction of a double bond into a steroid skeleton by overexpression of dehydrogenases is now described, which is characterized in that

- a) a dehydrogenase gene is isolated from a bacterium, cloned and amplified,
- b) promoter and terminator elements of the dehydrogenase gene or other promoter and terminator elements are isolated from the same or another bacterium, cloned and amplified,
- c) expression plasmids are designed in which the dehydrogenase gene from a), flanked by promoter and terminator sequences of the dehydrogenase gene or by other promoter and terminator elements from b), is contained,
- d) bacteria are transformed with the expression plasmid that is produced under c), and
- e) the thus produced bacteria are cultivated, and the selective dehydrogenation in the steroid skeleton is performed with these cultures, whereby
  - i) a high substrate concentration at unaltered operating times is used, and
  - ii) no disruptive secondary zones are produced.

This invention relates in particular to a process for selective introduction of a double bond into a steroid skeleton by overexpression of Δ¹-dehydrogenases, which is characterized in that

- a) a Δ¹-dehydrogenase gene is isolated from a bacterium, cloned and amplified,
- b) promoter and terminator elements of the Δ¹-dehydrogenase gene or other promoter and terminator elements are isolated from the same or another bacterium, cloned and amplified,
- c) expression plasmids are designed, in which the Δ¹-dehydrogenase gene from a), flanked by promoter and terminator sequences of the Δ¹-dehydrogenase gene of by other promoter and terminator elements from b), is contained,
- d) bacteria are transformed with the expression plasmid that is produced under c), and
- e) the thus produced bacteria are cultivated, and the selective dehydrogenation in the steroid skeleton is performed with these cultures, whereby
  - i) a high substrate concentration at unaltered operating times is used, and
  - ii) no disruptive secondary zones are produced

This invention relates in particular to a process for selective introduction of a double bond in a steroid skeleton by overexpression of 3-keto steroid-Δ¹-dehydrogenases, which is characterized in that

- a) the 3-keto steroid-Δ¹-dehydrogenase gene is isolated from a bacterium, cloned and amplified,
- b) promoter and terminator elements of the 3-keto steroid-Δ¹-dehydrogenase gene or other promoter and terminator elements are isolated from the same or another bacterium, cloned and amplified,
- c) expression plasmids are designed, in which the 3-keto steroid-Δ¹-dehydrogenase gene from a), flanked by promoter and terminator sequences of the 3-keto steroid-Δ¹-dehydrogenase gene or by other promoter and terminator elements from b), is contained,
- d) bacteria are transformed with the expression plasmid that is produced under c), and
- e) the thus produced bacteria are cultivated, and the selective dehydrogenation at 1-position in the steroid skeleton is performed with these cultures, whereby
  - i) a high substrate concentration at unaltered operating times is used, and
  - ii) no disruptive secondary zones are produced.

The bacteria that are mentioned in process steps a), b) and d) can be among the gram-positive genus Bacillus, such as Bacillus spec., Bacillus subtilis, Bacillus sphaericus, Bacillus megaterium, Bacillus licheniformis, Bacillus lentus as well as the gram-positive representatives Arthrobacter simplex and Brevibacterium maris or the gram-negative representatives Escherichia coli and Pseudomonas species.
This invention relates in particular to the 3-keto steroid-Δ¹-dehydrogenase gene from Arthrobacter simplex according to Seq. ID No. 1, the 3-keto steroid-Δ¹-dehydrogenase gene from Bacillus sphaericus with promoter and terminator elements according to Seq. ID No. 9 or Seq. ID No. 10, and the 3-keto steroid-Δ¹-dehydrogenase gene from Brevibacterium maris according to Seq. ID No. 12 as well as the correspondingly expressed proteins, such as 3-keto steroid-Δ¹-dehydrogenase from Bacillus sphaericus according to Seq. ID No. 11, 3-keto steroid-Δ¹-dehydrogenase from Brevibacterium maris according to Seq. ID No. 13 and 3-keto steroid-Δ¹-dehydrogenase from Arthrobacter simplex according to Seq. ID. No. 14.
The above-mentioned DNA sequences can be introduced into host cells with suitable plasmids. Suitable host cells or recipients are, e.g., gram-positive bacteria of the genus Bacillus that can be used for the overexpression of Δ¹-dehydrogenases with the purpose of dehydrogenating steroid molecules selectively in a biotransformation reaction. In particular, species such as Bacillus sphaericus and Bacillus subtilis are suitable for this purpose.
The bacteria are also subjects of this invention.
To introduce the inventive DNA sequences into the host cells, plasmids are used that contain at least one of the above-mentioned DNA sequences. In the plasmids, the Δ¹-dehydrogenase genes are provided with suitable promoters and terminators, which are necessary for overexpression in bacteria. Suitable promoter and terminators are, e.g., promoters and terminators of the 3-keto steroid-Δ¹-dehydrogenase gene of Bacillus sphaericus according to Seq. ID No. 9, constitutive promoters such as p(veg) or promoters of bacteriophages Φ29 and SPO1, inducible promoters such as p(aprE) or p(sacB) from Bacillus subtilis, hybrid promoters such as, e.g., a lacI-controlled SPO1-promoter, terminators of Escherichia coli such as t(rrnB) or of Bacillus subtilis such as t(senS) or t(senN) [see, i.a., Doi, R. H. (1984) In: Biotechnology and Genetic Engineering Reviews, Vol. 2, Russell, G. E. (ed.), Intercept, Newcastle Upon Tyne, UK, pp. 121-153; Le Grice, S. F. J. et al. (1986) In: Bacillus Molecular Genetics and Biotechnology Applications, Ganesan, A. T. and Hoch, J. A. (eds.), Academic Press, New York, 433-445; Mountain, A. (1989) hi: Bacillus, Harwood, C. R. (ed.), Plenum Press, New York, pp. 73-114; Le Grice, S. F. J. (1990) Meth Enzymol 185:210-214; Wang and Doi (1992) In: Biology of Bacilli: Applications to Industry, Doi et al. (eds.), Massachusetts, Butterworth-Heinemann, pp. 143-188].
The plasmids are also subjects of this invention.
The plasmids can be used for transformation of bacteria that are capable of overexpression of Δ¹-dehydrogenases.
The invention also relates to DNA sequences with 3-keto steroid-Δ¹-dehydrogenase activity, whose DNA sequences have a homology of more than 80%, especially a homology of more than 90%, and preferably a homology of more than 95%.
The invention also relates to protein sequences with 3-keto steroid-Δ¹-dehydrogenase activity that have a homology of at least 90%, especially a homology of at least 95%.
The invention also relates to promoters, especially the 3-keto steroid-Δ¹-dehydrogenase promoter from Bacillus sphaericus with the DNA sequence Seq. ID. No. 9, as well as homologous promoters that have a homology with Seq. ID No. 9 of more than 80%, preferably more than 90%, and especially preferably more than 95%.
The invention also relates to the Bacillus shaericus 3-keto steroid-Δ¹-dehydrogenase oligonucleotides according to sequences Seq. ID No. 15, Seq. ID No. 16, Seq. ID No. 17 and Seq. ID No. 18, and the parS oligonucleotides according to sequences Seq. ID No. 19 and Seq. ID No. 20 and use thereof in processes for selective introduction of double bonds into a steroid skeleton.
The DNA sequences and proteins according to the invention can be used for selective dehydrogenation of steroids. The DNA sequences and protein sequences are also subjects of this invention.
Dehydrogenated steroids are, e.g., betamethasone, clobetasone, clocortolone, Δ¹-11β,17α-dihydroxy-6α,9α-difluoro-16α-methylprogesterone, deflazacort, dexamethasone, diflocortolone, fluocinolone acetonide, fluocortolone, hydroxy acid and prednisolone and derivatives of the above-mentioned compounds.

Filings

The bacteria strains that are mentioned in the application can be ordered from the respective filing sites, e.g., from DSM
Deutsche Sammlung von Mikroorganismen und Zellkulturen [German Collection of Microorganisms and Cell Cultures] GmbH, Mascheroder Weg 1b, D-38124 Brunswick; ATCC
American Type Culture Collection, Rockville, Md., USA; NRRL
Northern Utilization Research and Development Division, Peoria, Ill., USA; etc.
To better understand the invention that is based on this invention, first the methods that are used are described.

1. Restrictions

Restrictions of plasmid DNA and genomic DNA were performed in volumes of 15 to 100 μl based on the amount of DNA that was used [1 to 20 μg]. The enzyme concentration was 1 to 5 units of restriction enzyme per μg of DNA. The reaction was performed in a buffer, incubated for one to three hours and subsequently analyzed on an agarose gel [Sambrook et al. (1989) Molecular Cloning: A Laboratory Manual, Cold Spring Harbor Laboratory Press, Cold Spring Harbor, N.Y.].

2. Agarose-Gel Electrophoresis

Gel electrophoreses were performed in Minigel-[BioRad], Midi-Widegel-[Biometra] and Maxigel devices [Biometra]. Depending on the separating problem, agarose gels with 0.8% to 4% [w/v] agarose in 0.5×TBE buffer were used. The electrophoresis was carried out with 0.5×TBE as a running buffer. DNA fragments were stained with ethidium bromide and made visible in a transilluminator [Sambrook et al. (1989) Molecular Cloning: A Laboratory Manual, Cold Spring Harbor Laboratory Press, Cold Spring Harbor, N.Y.]
3. Elution of DNA from an Agarose Gel
Preparative restriction preparations were separated in agarose gel according to size. The desired volumes were cut out with a scalpel. The DNA fragment to be isolated was recovered with the aid of the “Jetsorb Kit” [Genomed] taking into consideration the instructions of the manufacturer and taken up in TE buffer.

4. Phosphorylation of Oligonucleotides

50 pmol of oligonucleotide was incubated in buffer recommended by the manufacturer in the presence of 0.1 mmol of ATP and 20 units of T4 polynucleotide kinase for 45 minutes at 37° C. An enzyme inactivation was carried out at 68° C. [Sambrook et al. (1989) Molecular Cloning: A Laboratory Manual, Cold Spring Harbor Laboratory Press, Cold Spring Harbor, N.Y.].

5. Ligation

For ligation, suitable amounts of dephosphorylated, linearized vector-DNA and fragment-DNA were used in a molar ratio of 1:5. The reaction was carried out in a volume of 10 μl with 1 unit of T4-DNA-ligase in buffer recommended by the manufacturer at 16° C. overnight in a water bat [Sambrook et al. (1989) Molecular Cloning: A Laboratory Manual, Cold Spring Harbor Laboratory Press, Cold Spring Harbor, N.Y.].
6. Transformation of Escherichia coli
Competent E. coli cells were obtained by CaCl₂treatment and stored at −80° C. In general, a 10 μl ligation stock was incubated with 200 μl of competent cells. The transformation stocks were plated on LB agar with the addition of antibiotic necessary in each case and incubated for 16 hours at 37° C. Production of competent cells and a transformation were carried out according to Sambrook et al. (1989) Molecular Cloning: A Laboratory Manual, Cold Spring Harbor Laboratory Press, Cold Spring Harbor, N.Y.
7. Transformation of Bacillus subtilis
The transformation of Bacillus subtilis was carried out according to the two-stage process described by Cutting, S. M. and Vander Horn, P. B. [In: Molecular Biological Methods for Bacillus (1990), Harwood, C. R. and Cutting, S. M. (eds.), John Wiley & Sons, Chichester].
8. Transformation of Bacillus sphaericus
Bacillus sphaericus was transformed by electroporation in a way similar to a process published by Taylor and Burke (1990) [FEMS Microbiol Lett 66:125-1281. The cells were cultured overnight in MM2G medium [0.3% (w/v) meat extract, 0.8% (w/v) yeast extract, 1% (w/v) peptone, 0.2% (w/v) glucose, 0.7% (w/v) NaCl, 7.36 g/l of K₂HPO₄, 2.65 g/l of KH₂PO₄, 5 m/l of 100% glycerol, pH 7], 1:20 was transferred into fresh MM2G medium, and it was cultivated for 90 minutes at 37° C. and 250 rpm. The cells were pelletized, washed 3× with 10% glycerol and then taken up in 750 μl of glycerol. 50 μl of cell suspension was mixed in an electroporation cell with plasmid-DNA, incubated on ice, and placed in the electroporation device [Biorad Gene Pulser™] [2.5 kV, 25 μF, 600Ω]. The cells were incubated for regeneration for 90 minutes at 30° C. in MM2G medium and subsequently plated on TBAB agar/5 μg of neomycin [tryptose blood agar base (Difco)] and incubated for 24 hours at 30° C.
9. Plasmid Mini-Preparation from Escherichia coli
Mini-preparations were made according to the principle of alkaline cell lysis [Sambrook et al. (1989) Molecular Cloning: A Laboratory Manual, Cold Spring Harbor Laboratory Press, Cold Spring Harbor, N.Y.]. Individual colonies were cultured overnight in reagent glasses with 4 ml of LB medium and selection. 2 ml thereof was used for preparation.
10. Plasmid Mini-Preparation from Bacillus subtilis and Bacillus sphaericus
The preparation of plasmids from Bacillus subtilis and Bacillus sphaericus was carried out on columns of the Genomed Company [“Jetstar Kit Mini”] according to the protocol specified by the manufacturer. To ensure a complete cell lysis of the cells, the cell pellet that was taken up in buffer E1 was mixed with 5 mg/ml of lysozyme, and the cells were incubated for one hour at 37° C.
11. Plasmid Maxi-Preparation from Escherichia coli, Bacillus subtilis and Bacillus sphaericus
Plasmid maxi-preparation was made with the “Jetstar Kit Maxi” of the Genomed Company. The strains were cultivated overnight in 200 ml of LB medium in the presence of an antibiotic. The preparation of the plasmids was carried out according to the protocol specified by the manufacturer. To ensure a complete cell lysis of Bacillus subtilis and Bacillus sphaericus, the cell pellets that were taken up in buffer E1 were mixed in addition with 5 mg/ml of lysozyme, and the cells were incubated for one hour at 37° C.
12. Preparation of Genomic DNA from Arthrobacter simplex, Bacillus Species and Rhodococcus maris
200 ml of a densely-grown bacteria culture was pelletized and suspended in 11 ml of solution I [50 mmol of Tris-HCl, pH 8; 50 mmol of EDTA; 1% (v/v) Triton x-100, 200 μg/ml of Rnase]. The suspension was mixed with lysozyme [5 mg/ml→A. simplex, B. sp./15 mg/ml→R. maris] and 500 μl of proteinase K [20 mg/ml] and incubated for >30 minutes at 37° C. 4 ml of solution II [3 M guanidinium-hydrochloride, 20% (v/v) Tween] was subsequently added thereto, and the stock was incubated for 30 minutes at 50° C. Undissolved particles were pelletized and discarded. The chromosomal DNA that was dissolved in the lysate was purified by anionic exchange chromatography [“Jetstar Kit Maxi” of the Genomed Company, see the protocol specified by the manufacturer].

13. Polymerase Chain Reaction

The reaction conditions for the PCR were optimized for each individual case. In general, 0.1 to 0.5 μg of template-DNA, 10 mmol of dNTPs, 50 pmol each of 5′- and 3′-primer as well as 2.5 units of Pwo-polymerase [Boehringer Mannheim] were combined in the buffer recommended by the manufacturer in 100 μl of total volume. Depending on the template-DNA, the stock was added up to 10% DMSO. The PCR was performed in a “Biometra Trio Thermoblock.” The temperature profile was newly modified for each requirement. The annealing temperature varied between 50° C. [less stringent conditions] and 65° C. [See PCR 1: A Practical Approach, McPherson et al. (eds.), Oxford University Press (1991)]

14. Southern Analyses

In agarose gel, DNA that was separated according to size was transferred by the capillary-blot process [Sambrook et al. (1989) Molecular Cloning: A Laboratory Manual, Cold Spring Harbor Laboratory Press, Cold Spring Harbor, N.Y.] to positively-charged nylon membranes and linked covalently with the membrane by UV-irradiation.
Hybridizations were performed with digoxigenin-labeled probes. The labeling of the probes was carried out with the “DIG-High-Prime” or the “PCR DIG Probe Synthesis Kit” of Boehringer Mannheim according to the protocol recommended by the manufacturer.
For hybridization, an SDS-phosphate buffer was used [7% SDS (w/v); 0.5 M Na phosphate, pH 7.0]. Depending on the requirements, stringent or less stringent hybridization conditions were selected [Sambrook et al. (1989) Molecular Cloning: A Laboratory Manual, Cold Spring Harbor Laboratory Press, Cold Spring Harbor, N.Y.].
The detection of bonded DNA was carried out with a chemiluminescence reagent [CSPD®] of Boehringer Mannheim according to instructions recommended by the manufacturer.

14. Colony Hybridization

The transfer of colonies to Pall BIODYNE® A membranes [1.2 μm and 0.2 μm pore size] was performed according to the process recommended by the manufacturer.
The hybridization was carried out with digoxigenin-labeled probes in the above-indicated SDS-phosphate buffer, and the detection was carried out with a chemiluminescence reagent CSPD® of Boehringer Mannheim [“Pall Bio Support” application information SD1359G].

15. DNA-Sequence Analysis

DNA-sequence analyses were carried out with the GATC® 1500 system. The sequence reactions were performed with the GATC®-BioCycle Sequencing Kit according to the protocol recommended by the manufacturer and analyzed on a 4% polyacrylamide-urea gel [GATC® 1500-system protocol]. The detection was carried out with CSPD® [GATC®-BioCycle Sequencing Kit Protocol].
16. Hydrocortisone/Hydrocortisone-17-acetate→Prednisolone: Working-Up and Analysis
The culture broth was diluted with the 3× volume of methanol/1% acetic acid, ultrasound-treated and centrifuged off. The supernatant was chromatographed on an ODS-Hypersil column [250×4.6 mm] with an acetonitrile-water gradient at a flow rate of 1 ml/minute.
Sequence of eluants: hydrocortisone, prednisolone, 11β-hydroxyandrosta-1,4-diene-3,17-dione, hydrocortisone-17-acetate, hydrocortisone-21-acetate, prednisolone-21-acetate.
17. 4-Androstene-3,17-dione→Androsta-1,4-diene-3,17-dione: Working-Up and Analysis
Isobutyl methyl ketone extracts of the culture broth were analyzed by gas chromatography:
Column 1: 50 m×0.25 mm, Chrompack WCOT CP5 CB, film thickness 0.4 μm
Column 2: 30 m×0.25 mm, hp 1701, film thickness 0.4 μm
Detector: FID
Carrier gas: hydrogen
Preliminary column pressure: 175 kPa
Sequence of the eluants: 4-androstene-3,17-dione, androsta-1,4-diene-3,17-dione

18. Fluocortolone A Acetate→Fluocortolone: Working-Up and Analysis

The culture broth was set at pH 4-6 with acetic acid and then extracted with the 4× volume of isobutyl methyl ketone. The extract was concentrated by evaporation, taken up in chloroform and chromatographed on a Kromasil 100 column [250×4 mm] with an isocratic gradient of chloroform:isooctane:1,4-dioxane:ethanol:water 1000:100:50:10:2 at a flow rate of 1.2 ml/minute.
Sequence of eluants: fluocortolone A acetate, fluocortolone A, fluocortolone
19. 11β,17α-Dihydroxy-6α,9α-difluoro-16α-methylprogesterone→Δ¹-11β,17α-Dihydroxy-6α,9α-difluoro-16α-methylprogesterone: Working-Up and Analysis
The culture broth was diluted with the 3× volume of methanol/1% acetic acid, ultrasound-treated and centrifuged off. The supernatant was chromatographed on an ODS-Hypersil column [250×4.6 mm] with an acetonitrile-water gradient at a flow rate of 1 ml/minute.
Sequence of eluants: 11α,17α-Dihydroxy-6α,9α-difluoro-16α-methylprogesterone, Δ¹-11β,17α-Dihydroxy-6α,9α-di-fluoro-16α-methylprogesterone
20. 11β,21-Dihydroxy-2′-methyl-5′βH-pregn-4-eno[17,16-d]oxazole-3,20-dione→11β,21-Dihydroxy-2′-methyl-5′βH-pregna-1,4-dieno[17,16-d]oxazole-3,20-dione (Deflazacort Alcohol): Working-Up and Analysis
The culture broth was turraxed and then extracted with the 4× volume of methyl isobutyl ketone. The extract was evaporated to the dry state and taken up in the same volume of chloroform. The sample was applied on a Kromasil-100 column [250×4.6 mm] and chromatographed with diisopropyl ether:dichloroethane:1,4-dioxane:H₂O (250:150:75:4) at a flow rate of 2 ml/minute. Sequence of the eluants: 11β,21-dihydroxy-2′-methyl-5′βH-pregn-4-eno[17,16-d]oxazole-3,20-dione, 11β,21-dihydroxy-2′-methyl-5′βH-pregna-1,4-dieno[17,16-d]oxazole-3,20-dione (deflazacort alcohol)

DESCRIPTION OF THE FIGURES

FIGS. 1 a/1 b shows the alignment of all known 3-keto steroid-Δ¹-dehydrogenases

- [CLUSTAL, W. Algorithmus, Thompson, J. D. et al. (1994) Nucleic Acids Res 22:4673-4680].
- In the figure:
- Bm3os-delta1-DH means Brevibacterium maris 3-oxo steroid-Δ¹-dehydrogenase
- Rr3os-delta1-DH means Rhodococcus rhodochrous 3-oxo steroid-Δ¹-dehydrogenase
- As3os-delta1-DH means Arthrobacter simplex 3-oxo steroid-Δ¹-dehydrogenase
- Bs3os-delta1-DH means Bacillus sphaericus 3-oxo steroid-Δ¹-dehydrogenase
- Mt3os-delta1-DH means Mycobacterium tuberculosis 3-oxo steroid-Δ¹-dehydrogenase
- No3os-delta1-DH means Nocardia opaca 3-oxo steroid-Δ¹-dehydrogenase
- Ct3os-delta1-DH means Comamonas testosteroni 3-oxo steroid-Δ¹-dehydrogenase
- Number of perfect matches * 61
  10.34%
- Number of high similarity : 48
  8.14%
- Number of low similarity . 54
  9.15%
- Bm3os-delta1-DH [this work]; Rr3os-delta1-DH [GenBank AC: AB007847];
- As3os-delta1-DH [Molnar, I. et al. (1995) Mol Microbiol 15:895-905; GenBank AC: D37969]; Bs3os-delta1-DH [this work]; Mt3os-delta1-DH [cosmid Z82098, complement 16520 . . . 18211; http://www.sanger.ac.uk/M_tuberculosis]; No3os-delta1-DH [Drobnic, K. et al. (1993) Biochem Biophys Res Comm 190:509-515; SUISS-PROT AC: Q04616]; Ct3os-delta1-DH [Plesiat P. et. (1991) J Bacteriol 173:7219-7227; SUISS-PROT AC: Q06401].

FIG. 2 shows expression plasmid TS#196

FIG. 3 shows the reaction of EAF/MAF/F to form Pln [1 g/l]: cf. strain

- AD#67 with Bacillus sphaericus ATCC 13805
- In the figure:
- EAF
  Hydrocortisone-21-acetate
- MAF
  Hydrocortisone-17-acetate
- F
  Hydrocortisone
- Pln
  Prednisolone

FIG. 4 shows the reaction of EAF/MAF/F to form Pln [10 g/l]: cf. strain

FIG. 5 shows the reaction of AD to form ADD [1 g/l]: cf. strain AD#67 with Bacillus sphaericus ATCC 13805

- In the figure:
- AD
  4-Androstene-3,17-dione
- ADD
  Androsta-1,4-diene-3,17-dione

FIG. 6 shows the reaction of FCAA to form FC [1 g/l]: cf. strain AD#116 with Bacillus sphaericus ATCC 13805

- In the figure:
- FCAA
  Fluocortolone A acetate
- FCA
  Fluocortolone A
- FC
  Fluocortolone

FIG. 7 shows the reaction of DDFMP to form Δ¹-DDFMP [0.2 g/l]: cf. strain

- AD#116 with Bacillus sphaericus ATCC 13805
- In the figure:
- DDFMP
  11β,17α-Dihydroxy-6α,9α-difluoro-16α-methylprogesterone
- Δ¹-DDFMP
  Δ¹-11β,17α-Dihydroxy-6α,9α-difluoro-16α-methylprogesterone

FIG. 8 shows the conversion of EAF/MAF/F to Pln in 10 l of fermenter [20 g/l]

- Cf. strain AD#67/ Bacillus sphaericus ATCC 13805
- For the meaning of the abbreviations, see above.

FIG. 9 shows the reaction of 11β,21-dihydroxy-2′-methyl-5′βH-pregn-4-eno[17,16-d]oxazole-3,20-dione to form 11β,21-dihydroxy-2′-methyl-5′βH-pregna-1,4-dieno[17,16-d]oxazole-3,20-dione (deflazacort alcohol) [1 g/L]: cf. strain

- AO#205 with Bacillus sphaericus ATCC 13805

The cloning, isolation and construction examples below describe the biological feasibility of the invention, without limiting the latter to the examples.

EXAMPLE 1

Cloning of the 3-Keto Steroid-Δ¹-Dehydrogenase Genes from Various Species

1.1 From Arthrobacter simplex ATCC 6946
To isolate the 3-keto steroid-Δ¹-dehydrogenase gene from Arthrobacter simplex ATCC 6946, the open reader frame was amplified in a PCR reaction with the primer pair 2026[5′ GGG GAT CCA TGG ACT GGG CAG AGG AGT ACG ACG TAC TGG TGG_1435-1468]and 2027 [5′ CGG AAT TCT CAT CGC GCG TCC TCG GTG CCC ATG TGC CGC ACG_2982-2949] from genomic DNA of Arthrobacter simplex. The amplified gene was cloned as an NcoI-EcoRI fragment in the corresponding interfaces of vector pTrc99A [Pharmacia] or as a BamHI-EcoRI fragment in the corresponding interfaces of plasmid pSP72 [Promega]. The gene sequence was verified with a GATC® 1500 Sequencer [GATC].
1.2 From Bacillus sphaericus ATCC 13805
To isolate the 3-keto steroid-Δ¹-dehydrogenase gene from Bacillus sphaericus ATCC 13805, a homologous probe from genomic DNA of Bacillus sphaericus was isolated with use of degenerated primers in a PCR reaction: under less stringent conditions, a 1463 bp fragment was amplified with the primer pair 2048 [5′ GAA TRY GAT NTW NTW GTW GYW GGW WSW GG] and 2054 [5′ NAR NCC NCC YTT NGT NCC] and cloned in pCRScript™ Amp SK(+) [Stratagene]. With the insert as a DNA probe, overlapping genomic clones from a DNA library, which had been produced with the use of Zero Background™/Kan Cloning Kits [Invitrogen], were isolated. The sequence of the Bacillus sphaericus 3-keto steroid-Δ¹-dehydrogenase gene was determined with a GATC® 1500 sequencer [GATC]. The protein sequence derived from the gene sequence is 34% identical to the sequence of the 3-keto steroid-Δ¹-dehydrogenase from Comamonas testosteroni. The similarity is 54%. A 34% identity and a 54% similarity exist in the 3-keto steroid-Δ¹-dehydrogenase from Arthrobacter simplex.
1.3 From Brevibacterium maris ATCC 21111
To isolate the 3-keto steroid-Δ¹-dehydrogenase gene from Brevibacterium maris ATCC 21111, first heterologous DNA probes were isolated from the 3-keto steroid-Δ¹-dehydrogenase gene of Arthrobacter simplex and DIG-labeled: a 109 bp fragment [2066-2175] was amplified with the primer pair 2017 [GAC GCC GTA CTT CTG GCG GAG CTC GTC ATT GGC C_2175-2142] and 2032 [CGA TCG TCG AGA CCG ACG G_2066-2084], a 190 bp fragment [1428-1618] was amplified with the primer pair 2016 [GAT CAC GAT GGA CTG GGC AGA GGA GTA CGA CG_1428-1459] and 2055 [GCA GCA CCG GGT TCG CGG GGA ACC AGG_1618-1592], and a 747 bp fragment [1428-2175] was amplified with the primer pair 2016 and 2017. In Southern analyses, subsequent specific binding of the above-mentioned probes to Brevibacterium maris DNA was detected. The conditions were used to identify clones with 3-keto steroid-Δ¹-dehydrogenase gene sequences in a DNA library of Brevibacterium maris, which had been produced with use of Zero Background™/Kan Cloning Kits [Invitrogen]. In this connection, two overlapping clones were identified. The sequence of the Brevibacterium maris 3-keto steroid-Δ¹-dehydrogenase gene was determined. The protein sequence derived from the gene sequence is 28% identical to the sequence of the 3-keto steroid-Δ¹-dehydrogenase from Comamonas testosteroni. The similarity is 44%. A 72% identity and an 83% similarity exist in the 3-keto steroid-Δ¹-dehydrogenase from Arthrobacter simplex.
A comparison of all known 3-keto steroid-Δ¹-dehydrogenases, including new sequences that are described here, yields—relative to the length of the consensus, an identity of only 10% and a similarity of only 18% [FIG. 1].

1.4 From Mycobacterium Species NRRL B-3683

For cloning the 3-keto steroid-Δ¹-dehydrogenase gene from Mycobacterium species NRRLB-3683, first, analogously to the above, binding to Mycobacterium sp. DNA was detected with the described DNA probes, and the gene was then isolated from a genomic DNA library.

1.5 From Mycobacterium Species NRRL B-3805

For cloning the 3-keto steroid-Δ¹-dehydrogenase gene from Mycobacterium species NRRLB-3805, first binding to Mycobacterium sp. DNA was detected analogously to the above with the described DNA probes, and the gene was then isolated from a genomic DNA library.

EXAMPLE 2

Isolating and Characterizing the Promoter and Terminator Sequences

As regulatory sequences for the overexpression of the 3-keto steroid-Δ¹-dehydrogenase genes, promoter and terminator elements of the 3-keto steroid-Δ¹-dehydrogenase gene from Bacillus sphaericus were used. Both elements were isolated and characterized in line with the cloning of the gene.
The promoter at position 84 bp or 61 bp above the startcodon contains two hexanucleotides [TTGACT_{−84 to −79}/TATACT_{−61 to −56}], which correspond, with a deviation in each case, to the consensus of bacterial promoters [−10/−35 Box]. The distance from 17 nucleotides of the two elements to one another corresponds exactly to the bacterial consensus [see Record, M. T. et al. (1996) In: Escherichia coli and Salmonella, Neidhardt, F. C. (ed.), 2^ndEdition, ASM Press, Washington D.C., Vol. 1, pp. 792-821].
16 bp above the startcodon lies a ribosome-binding site that is typical of Bacillus [AGGGAGG_{−16 to −10}; Band, L. and Henner, D. J. (1984) DNA 3: 17-21].
Promoter activity was detected for fragments from position −126 [SalI] to position −28 [ClaI] and from position −258 [PstI] to position −28 [ClaI] in lacZ assays.
9 bp behind the stopcodon is a palindrome [AAGCCCTTCCT_1698-1708/AGGAAGGGCT_1731-1741], which acts as a ρ-independent terminator [see Richardson, J. P. and Greenblatt, J. (1996) In: Escherichia coli and Salmonella, Neidhardt, F. C. (ed.), 2^ndEdition, ASM Press, Washington D.C., Vol. 1, pp. 822-848].
In principle, other promoters and terminators can also be used [see, i.a., Doi, R. H. (1984) In: Biotechnology and Genetic Engineering Reviews, Vol. 2, Russell, G. E. (ed.), Intercept, Newcastle Upon Tyne, UK, pp. 121-153; Le Grice, S. F. J. et al. (1986) In: Bacillus Molecular Genetics and Biotechnology Applications, Ganesan, A. T. and Hoch, J. A. (eds.), Academic Press, New York, 433-445; Mountain, A. (1989) In: Bacillus, Harwood, C. R. (ed.), Plenum Press, New York, pp. 73-114; Le Grice, S. F. J. (11990)Meth Enzymol 185:210-214; Wang and Doi (1992) In: Biology of Bacilli: Applications to Industry, Doi et al. (eds.), Massachusetts, Butterworth-Heinemann, pp. 143-188].

EXAMPLE 3

Construction of Expression Plasmids

For the production of an expression plasmid, first a “shuttle” plasmid that consists of pSP72 [Promega] and portions of pUB110 [McKenzie et al. (1986) Plasmid 15:93-103] was designed. To this end, pUB110 was cleaved with EcoRI and PvuII, and the resulting 3.6 kb fragment was inserted in the EcoRI and EcoRV interfaces of pSP72. The 3-keto steroid-Δ¹-dehydrogenase gene of Bacillus sphaericus, flanked by promoter and termination sequences [Position −126 (Sail) to Position 1861 (ScaI)], was ligated as an XbaI-ScaI fragment in the XbaI and PvuII interfaces of the above-described “shuttle” vector [→TS#196, see FIG. 2].
A second expression plasmid carries a modified Δ¹-dehydrogenase gene promoter p(Δ¹)_mut: By PCR-mutagenesis, in each case a base was exchanged in the −35 [TTGACT→TTGACA] and in the −10 Box [TATACT→TATAAT] to achieve an exact correspondence to the consensus of bacterial promoters. For this purpose, the promoter was first amplified with the mutagenesis primer 2089_mut[CCA TCG ATG AAT CTG GTC TTC CTA TTA AAA ATT ATA GAA TTA AAC TAA TAT TCT GTC AAT TTT TCC_{−29 to −91}] and primer 2090 [CAT GAC AAA ATT ATT TGA TTT AAT CAC_{−258 to −284}] and inserted as a PstI-ClaI fragment into the corresponding interfaces of pBluescript II KS(+). The mutations were verified by sequence analysis. p(Δ¹)_mutwas cut out as an XbaI-ClaI fragment and ligated in the corresponding interfaces of TS#196. In this connection, the wt promoter was exchanged for p(Δ¹)_mut[→TS#251].
In addition, two other plasmids carry a plasmid-stabilizing signal, parS [Lin, D. C. and Grossman, A. D. (1998) Cell 92:675-685]. The latter was cloned via two oligonucleotides that are complementary to one another, 2091_parS[GAT CCT GTT CCA CGT GAA ACA G] and 2092_parS[GAT CCT GTT TCA CGT GGA ACA G], in the BamHI interface of TS#196 [→AD#82] and TS#251 [→TS#255].
For expression in Escherichia coli DH5α[≡DSM 6897], the 3-keto steroid-Δ¹-dehydrogenase gene of Bacillus sphaericus, flanked by promoter and termination sequences, was cloned as a 2865 bp SalI-partial Sau3A fragment [position −126 to position 2739] in the plasmid pZErO™-2 that is cut with BamHI and XhoI and transformed into Escherichia coli DH5α [→plasmid MS#46 or; strain MS#46_MS#461].

EXAMPLE 4

Production of Recombinant Strains of the Genus Bacillus for the Introduction of a Δ¹-Dehydrogenation on the Steroid

Expression plasmids TS#196, TS#251, AD#82 and TS#255 were transformed into Bacillus subtilis DSM 402 [Deutsche Stammsammlung fir Mikroorganismen [German Strain Collection for Microorganisms], Brunswick] and Bacillus sphaericus ATCC 13805. Bacillus subtilis and Bacillus sphaericus are gram-positive, apathogenic organisms. They are simple to cultivate. In contrast to Bacillus sphaericus, Bacillus subtilis is well characterized in molecular-genetic terms. There are a number of examples for the heterologous expression and secretion of proteins for the production of recombinant gene products [Wang and Doi (1992) In: Biology of Bacilli: Applications to Industry, Doi et al. (eds.), Massachusetts, Butterworth-Heinemann, pp. 143-188]. Suitable promoters and terminators are also described here.
With some of the recombinant strains, reactions of a mixture of hydrocortisone [F], hydrocortisone-17-acetate [MAF] and hydrocortisone-21-acetate [EAF] to form prednisolone [Pln] were performed by way of example in a shaking flask. In addition to starting substances F, MAF and EAF as well as the desired product Pln, the formation of prednisolone-21-acetate [Pln-21-acetate] and the undesirable secondary zone 11β-hydroxyandrosta-1,4-diene-3,17-dione [11 β-OH-ADD] was also tracked. To demonstrate the reaction potential of the recombinant strains, the process was performed at substrate concentrations in which Bacillus sphaericus ATCC 13085 forms no more than 20% Pln.
The strains AD#67_TS#196, AD#94_TS#251, AD#95_TS#255, AD#96_TS#255, AD#116_TS#251, and AO#205_TS#196are produced from Bacillus sphaericus ATCC 13085 and in each case contain the indicated expression plasmid. Strains AD#89_TS#196and AD#90_TS#196are produced from Bacillus subtilis DSM 402 and in each case contain the indicated expression plasmid.
The following reaction examples describe the microbiological feasibility of the invention, without the latter being limited to the examples.

EXAMPLE 1

Reaction of EAF/MAF/F to Form Pln

Bacillus sphaericus ATCC 13805, AD#67_TS#196, AD#94_TS#251, AD#95_TS#255, AD#96_TS#255, AD# 116 _TS#251 , Bacillus subtilis DSM 402, AD#89_TS#196, AD#90_TS#196 , Escherichia colt DH5α DSM 6897 and MS#46_MS#46were cultivated in LB medium [Sambrook et al. (1989) Molecular Cloning: A Laboratory Manual, Cold Spring Harbor Laboratory Press, Cold Spring Harbor, N.Y.] in the presence of 5 μg/ml of neomycin [Bacillus sphaericus derivatives], 50 μg/ml or 100 μg/ml of kanamycin [Escherichia coli or Bacillus subtilis derivatives] or without the addition of an antibiotic [wt-strains] at 37° C. and 220 rpm. In the reaction of EAF/MAF/F to form Pln, the inoculation material 1:10 in fresh LB medium was converted without the addition of antibiotic, and the culture was shaken as above. In principle, any other medium in which the organism can grow can also be used. Substrate was added after 3 hours. After 24 hours, the flasks were removed, and educts and product(s) were extracted and HPLC-analyzed [see Table 1; reaction diagram, see below]. Bacillus subtilis DSM 402 and Escherichia coli DH5α, as expected, do not show any reaction, Bacillus sphaericus ATCC 13085 forms less than 20% product after 24 hours, while all recombinant strains of the genus Bacillus [AD#67_TS#196, AD#94_TS#255, AD#95_TS#255, AD#96_TS#255, AD#89_TS#196and AD#90_TS#196] produce more than 80% Pln in the same period. A degradation of substrate or product over 48 hours could not be observed.
All tests that are described below were performed by way of example with AD#67_TS#196or AD#116_TS#251. As a standard, Bacillus sphaericus ATCC 13085 was used. The tests show the reaction activity, increased by a multiple, of the above-mentioned recombinant strains with respect to Δ¹-dehydrogenations on the steroid molecule.

EXAMPLE 2

Kinetics of the Reaction of EAF/MAF/F to Form Pln [1 g/l]

First, a Δ¹-dehydrogenation in the example of a reaction of EAF/MAF/F to form Pln was performed analogously to the above at a substrate concentration of 1 g/l in a shaking flask [LB medium, 37° C., 220 rpm]. The addition of substrate was carried out after 3 hours. To be able to track the course of the reaction, samples were taken after 4, 5, 6, 7, 8, 9, 10, 11, 12 and 24 hours, and educts and products were extracted and HPLC-analyzed. While the strain ATCC 13805 requires 24 hours to convert the substrate completely into Pln, strain AD#67 has already formed the corresponding amount of Pln after <10 hours [FIG. 3; reaction diagram, see below].

EXAMPLE 3

Kinetics of the Reaction of EAF/MAF/F to Form Pln [10 g/l]

The same test was performed at a substrate loading of 10 g/l. The substrate was added after 3 hours, samples were taken after 6, 9, 12, 24, 30 and 36 hours, and the steroids were extracted and analyzed. After 6 hours, the ATCC 13085 culture has only 1% Pln, while the strain AD#67 has already formed >15% product. After 12 hours, strain AD#67 has already converted more than 50% of the substrate into Pln; strain TCC 13805, however, has converted only 5% [FIG. 4; reaction diagram, see below].
The high reaction activity of strain AD#67 is not limited to the process for the production of prednisolone from EAF/MAF/F but rather applies in general to the introduction of Δ¹into a steroid molecule.

EXAMPLE 4

Conversion of 4-Androstene-3,17-dione [AD] into Androsta-1,2-diene-3,17-dione [ADD]

The conversion of AD into ADD by strain AD#67 or strain ATCC 13805 was studied analogously to the above in a shaking flask [LB medium, 37° C., 220 rpm]. The substrate was added after 3 hours, and samples were taken after 4, 5, 6, 7, 9 and 10 hours. As in the conversion of MAF/F into Pln, the product formation is carried out considerably faster in the case of fermentation with strain AD#67 than with use of strain ATCC 13805. After 10 hours, Bacillus sphaericus ATCC 13805 has converted less than 30% of the substrate to ADD, while in strain AD#67 at this time, already more than 70% of product could be isolated [FIG. 5].

EXAMPLE 5

Reaction of Fluocortolone A Acetate [FCAA] to Form Fluocortolone [FC]

Fluorinated steroids are also dehydrogenated by recombinant strains considerably more efficiently in 1-position than was heretofore possible with the available bio-catalysts. This shows the conversion of FCAA to FC analogously to the above in a shaking flask by AD#116 in comparison to Bacillus sphaericus ATCC 13805 [FIG. 6; reaction diagram, see below].

EXAMPLE 6

Reaction of 11β,17α-Dihydroxy-6α,9α-difluoro-16α-methylprogesterone [DDFMP] to Form Δ¹-11β,17α-Dihydroxy-6α,9α-difluoro-16α-methylprogesterone [Δ¹DDFMP]

The conversion of DDFMP to Δ¹DDFMP analogously to the above-mentioned examples is also carried out considerably more efficiently with AD#116 than with Bacillus sphaericus ATCC 13805 [FIG. 7, reaction diagram, see below].

EXAMPLE 7

Conversion of EAF/MAF/F to Form Pln in a 10 l Fermenter [20 g/l] Cf. Strain A)#67/ Bacillus sphaericus ATCC 13805

The Δ¹-dehydrogenation capacity of strain AD#67 was tested in comparison to Bacillus sphaericus ATCC 13805 in the example of EAF/MAF/F→Pln in 10 l of fermenter. The reaction was performed in a 20× higher substrate loading. The culture of the inoculation material was carried out in a first step overnight at 37° C. and 220 rpm in LB medium in the presence of 5 μg/ml of neomycin [AD#67] or without the addition of an antibiotic [ATCC 13805]. Subsequently, the overnight culture 1:100 was converted into a 1000 ml intermediate culture and shaken for 9 hours at 37° C. and 220 rpm to an optical density of 2.4. The fermentation was carried out in LB medium without the addition of an antibiotic. In principle, however, any other medium in which the organism can grow can be used. After 3 hours, the substrate was added continuously for 30 hours. The pH was kept at 8. In the course of the fermentation, samples were taken and tested for the content of product and educt. The fermentation profile shows that Bacillus sphaericus ATCC 13805 cannot surmount substrate concentrations of this order of magnitude: the reaction stops when more than 80% substrate remains. The conversion capacity of strain AD#67, however, is considerable: Shortly after the substrate application phase has ended, the reaction is almost fully [>98%] completed [FIG. 8]. The conversion activity of strain AD#67 is approximately 0.6 g/l per hour. Strain ATCC 13805 shows, however, an activity of 0.1 g/l per hour. In any case, disruptive secondary zones such as, e.g., 11-β-OH-ADD, were observed in traces. The crystal yield of Pln was approximately over 80% of theory and corresponds to the value that is achieved in conventional processes [reaction diagram, see below].

EXAMPLE 8

Reaction of 11β,21-Dihydroxy-2′-methyl-5′βH-pregn-4-eno[17,16-d]oxazole-3,20-dione to form 11β,21-dihydroxy-2′-methyl-5′βH-pregna-1,4-dieno[17,16-d]oxazole-3,20-dione (deflazacort alcohol)

The conversion of 1 g/l of 11β,21-dihydroxy-2′-methyl-5′βH-pregn-4-eno[17,16-d]oxazole-3,20-dione to deflazacort alcohol in a shaking flask analogously to the above-mentioned examples is carried out significantly more efficiently with AO#205 than with Bacillus sphaericus ATCC 13805 [FIG. 9; reaction diagram, see below]. Unlike in the above, a medium that consists of 12 g/l of 67% yeast extract, 27 g/l of corn steep liquor and 9.2 g/l of NaCl was used.

TABLE 1

		EAF/MAF	Pln	11β-OH-ADD	Substrate
Strain	F [mg/l]	[mg/l]	[mg/l]	[mg/l]	Loading

Bacillus sphaericus
ATCC
13805^a)	7720	39	1730	<10	9 g/l
AD#
67_TS#196 ^a)	1570	22	7790	<10	9 g/l
AD#94_TS#251 ^a)	1650	30	7480	13	9 g/l
AD#95_TS#255 ^a)	1460	18	7500	13	9 g/l
AD#96_TS#255 ^a)	1530	19	7130	13	9 g/l
AD#
116_TS#251	2150	n.d.^b)	9330	<10	12 g/l
Bacillus subtilis
DSM 402^a)	9030	510	<1	<10	9 g/l
AD#89_TS#196	1820	500	8280	14	10 g/l
AD#
90_TS#196	1680	580	8120	<10	10 g/l
Escherichia coli
DH5α	11110	1020	<1	n.d.^b)	12 g/l
MS#46_MS#46	9510	1080	1910	n.d.^b)	12 g/l

^a)Double determination
^b)Not determined

Claims

1.-39. (canceled)

40. A process for the selective introduction of a double bond into ring A of a steroid skeleton by overexpression of 3-keto steroid-Δ¹-dehydrogenases, comprising

a) isolating a Δ¹-dehydrogenase gene from Arthrobacter simplex comprising Seq. ID No. 1, a sequence having at least 90% homology to Seq. ID No. 1, Seq. ID No. 14 or a sequence having at least 90% homology to Seq. ID No. 14, and cloning and amplifying said gene,

b) isolating a promoter and a terminator element of the 3-keto steroid-Δ¹-dehydrogenase gene or another promoter and terminator element from the same or another bacterium, and cloning and amplifying said elements,

c) constructing an expression plasmid comprising the 3-keto steroid-Δ¹-dehydrogenase gene from a), flanked by promoter and terminator sequences of the 3-keto steroid-Δ¹-dehydrogenase gene or by another promoter and terminator element from b),

d) transforming host bacteria with the expression plasmid that is produced under c), and

e) cultivating the thus produced bacteria to dehydrogenate at the 1-position in the steroid skeleton, wherein

i) a high substrate concentration at unaltered operating times is used, and

ii) no disruptive secondary zones are produced.

41. A process for selective introduction of a double bond into ring A of a steroid skeleton by overexpression of 3-keto steroid-Δ¹-dehydrogenases, wherein

a) isolating an Δ¹-dehydrogenase gene from Brevibacterium maris comprising Seq. ID No. 12, a sequence having at least 90% homology to Seq. ID No. 12, Seq. ID No. 13 or a sequence having at least 90% homology to Seq. ID No. 13, cloning and amplifying said gene,

b) isolating a promoter and a terminator element of the 3-keto steroid-Δ¹-dehydrogenase gene or isolating another promoter and terminator element from the same or another bacterium, cloning and amplifying said element,

c) constructing an expression plasmid in which the 3-keto steroid-Δ¹-dehydrogenase gene from a) is flanked by a promoter and a terminator sequence of the 3-keto steroid-Δ¹-dehydrogenase gene or by another promoter and terminator element from b),

d) transforming a host bacteria with the expression plasmid that is produced under c), and

i) cultivating the thus produced bacteria, and selectively dehydrogenating the 1-position in the steroid skeleton, wherein

ii) a high substrate concentration at unaltered operating times is used, and no disruptive secondary zones are produced.

42. A process according to claim 40, wherein said promoter comprises Seq. ID No. 9 or a sequence having at least 90% homology to Seq. ID No. 9.

43. A process according to claim 41, wherein said promoter comprises Seq. ID No. 9 or a sequence having at least 90% homology to Seq. ID No. 9.

44. A process according to claim 40, wherein said dehydrogenated steroid is betamethasone, clobetasone, clocortolone, Δ¹-11β,17α-dihydroxy-6α,9α-difluoro-16α-methylprogesterone, deflazacort, dexamethasone, diflocortolone, fluocinolone acetonide, fluocortolone, hydroxy acid or prednisolone and/or derivatives thereof.

45. A process according to claim 41, wherein said dehydrogenated steroid is betamethasone, clobetasone, clocortolone, Δ¹-11β,17α-dihydroxy-6α,9α-difluoro-16α-methylprogesterone, deflazacort, dexamethasone, diflocortolone, fluocinolone acetonide, fluocortolone, hydroxy acid or prednisolone and/or derivatives thereof.

46. A process according to claim 40, wherein said steroid skeleton is hydrocortisone (F), hydrocortisone-17-acetate (MAF), hydrocortisone-21-acetate (EAF), 4-androstene-3-17-dione (AD), fluocortolone A acetate (FCAA) or 11β,17α-Dihydroxy-6α,9α-difluoro-16α-methylprogesterone (DDFMP).

47. A process according to claim 41, wherein said steroid skeleton is hydrocortisone (F), hydrocortisone-17-acetate (MAF), hydrocortisone-21-acetate (EAF), 4-androstene-3-17-dione (AD), fluocortolone A acetate (FCAA) or 11β,17α-Dihydroxy-6α,9α-difluoro-16α-methylprogesterone (DDFMP).

48. A process according to claim 42, wherein said steroid skeleton is hydrocortisone (F), hydrocortisone-17-acetate (MAF), hydrocortisone-21-acetate (EAF), 4-androstene-3-17-dione (AD), fluocortolone A acetate (FCAA) or 11β,17α-Dihydroxy-6α,9α-difluoro-16α-methylprogesterone (DDFMP).

49. A process according to claim 40, wherein said promoter or terminator is a constitutive promoter that is p(veg), a promoter of bacteriophages Φ29 or SPO1, an inducible promoter that is p(aprE) or p(sacB) from Bacillus subtilis, a hybrid promoter that is a lacI-controlled SPO1-promoter, a terminator of Escherichia coli that is t(rrnB) or of Bacillus subtilis that is t(senS) or t(senN).

50. A process according to claim 41, wherein said promoter or terminator is a constitutive promoter that is p(veg), a promoter of bacteriophages Φ29 or SPO1, an inducible promoter that is p(aprE) or p(sacB) from Bacillus subtilis, a hybrid promoter that is a lacI-controlled SPO1-promoter, a terminator of Escherichia coli that is t(rrnB) or of Bacillus subtilis that is t(senS) or t(senN).

51. A process of claim 40, wherein said terminator is the terminator of the 3-Keto steroid-Δ¹-dehydrogenase gene from Bacillus sphaericus comprising SEQ ID NO: 10.

52. A process of claim 41, wherein said terminator is the terminator of the 3-Keto steroid-Δ¹-dehydrogenase gene from Bacillus sphaericus comprising SEQ ID NO: 10.

53. A process of claim 40, wherein said host cell is B. sphaericus, B. subtilis or E. coli.

54. A process of claim 41, wherein said host cell is B. sphaericus, B. subtilis or E. coli.