Transformation of steroids by Mucor griseo-cyanus

Production of 14α-hydroxysteroids by a recombinant Saccharomyces cerevisiae biocatalyst expressing of a fungal steroid 14α-hydroxylation system

The 14α-hydroxysteroids have specific anti-gonadotropic and carcinolytic biological activities and can be produced by microbial biotransformation. The steroid 11β-/14α-hydroxylase P-450_lun from Cochliobolus lunatus is the only fungal cytochrome P450 enzyme identified to date with steroid C14 hydroxylation ability. Previous work has mainly revealed the 11β-hydroxylation activity of the P-450_lun towards cortexolone (RSS) substrate; however, the potential steroid 14α-hydroxylation activity of this enzyme, especially for androstenedione (AD) substrate, has not yet conducted in-depth testing. In this work, we further tested the steroid 14α-hydroxylation activity of the P-450_lun towards RSS and AD in the Saccharomyces cerevisiae system. We demonstrated that P-450_lun functions as the specific 14α-hydroxylase towards the AD substrate (regiospecificity > 99%); however, it showed a poor C14-hydroxylation regiospecificity (around 40%) for the RSS substrate. In addition, through transcriptome analysis combined with gene functional characterizations, we also identified and cloned the gene for the P-450_lun-associated redox partner CPR_lun. Finally, through codon optimization, knockout of genes for the side reactions related enzymes GCY1 and YPR1, and increasing copies of the P-450_lun and CPR_lun, we developed a recombinant S. cerevisiae biocatalyst based on the C. lunatus steroid 14α-hydroxylation system to produce 14α-hydroxysteroids. Initial production of 14α-OH-AD (150 mg/L day productivity, 99% regioisomeric purity, and 60% w/w yield) and 14α-OH-RSS (64 mg/L day productivity, 40% regioisomeric purity, and 26% w/w yield) were separately achieved in shake flasks; these results represent the highest level of 14α-hydroxysteroid production in the current yeast system.

Mucor hiemalis mediated 14α-hydroxylation on steroids: in vivo and in vitro investigations of 14α-hydroxylase activity

Transformation of testosterone and progesterone into synthetically challenging 14α-hydroxy derivatives was achieved by using fungal strain Mucor hiemalis. Prolonged incubation led to the formation of corresponding 6β/7α,14α-dihydroxy metabolites. The position and stereochemistry of newly introduced hydroxyl group was determined by detailed spectroscopic analyses. The time course experiment indicated that fungal strain initiated transformation by hydroxylation at 14α-position followed by at 6β- or 7α-positions. Studies using cell-free extracts suggest that the 14α-hydroxylase activity is NADPH dependent and belongs to the cytochrome P450 family.

Microbial models of drug metabolism: microbial transformations of Trimegestone (RU27987), a 3-keto-delta(4,9(10))-19-norsteroid drug

Screening microorganisms for the biotransformation of the 3-keto-delta(4,9(10))-19-norsteroid RU27987 (Trimegestone) resulted in the isolation of nine identified metabolites, some of them being selectively produced by different strains. Eight metabolites were found to be hydroxylated on various positions of the rings, and one was additionally epoxidized. These microbial metabolites could be used as chromatographic standards and two of them were found identical to the unknown major human metabolites. Moreover, most microbial metabolites were produced in sufficient amounts to be tested for their biological activities. All these features demonstrate the usefulness and versatility of microbial biotransformation systems as a tool for early identification and convenient production of potentially active mammalian and non-mammalian metabolites.

Biotransformation XXXIX. Metabolism of testosterone, androstenedione, progesterone and testosterone derivatives in Absidia coerulea culture

The strain of Absidia coerulea was used to investigate the transformations of testosterone, androstenedione, progesterone and testosterone derivatives with additional Cl-C2 double bond and/or 17alpha-methyl group. All the examined substrates were transformed, mainly hydroxylated. It was found that the position and stereochemistry of the introduced hydroxyl group, as well as the yield of products, depended on the structure of the substrate. The first three substrates (hormones) underwent hydroxylation at C-14, and additional hydroxylation at 7alpha was observed in progesterone. The presence of the double bond (C1-C2) in 1-dehydrotestosterone did not influence the position of hydroxylation, but the product with additional C14-C15 double bond (at the same site as hydroxylation) was formed. 17alpha-Methyltestosterone was hydroxylated at the 7alpha position, and also the dehydrogenated product (at the same site, with C6-C7 double bond) was obtained. The testosterone derivative with both C1-C2 double bond and 17alpha-methyl group underwent hydroxylation at the 7alpha or 11beta position, and a little amount of 14alpha, 15alpha epoxide was formed.

Microbial transformation of steroids: contribution to 14 alpha-hydroxylations

The regioselective and stereoselective hydroxylation of steroids by fungal strains previously known for their hydroxylation capabilities, such as Thamnostylum (= Helicostylum) piriforme ATCC 8992, Mucor griseocyanus ATCC 1207a, Actinomucor elegans (= Mucor parasiticus) MMP 3122 (Mucorales), and Zygodesmus sp. ATCC 14716, was investigated with special interest for the 14 alpha-hydroxylation reaction. A preliminary screening had shown that some of these microorganisms were adequate for the production of 14 alpha-hydroxylated derivatives of the following steroids: progesterone, 5 beta-pregnane-3,20-dione, 3 beta-hydroxy-5 beta-pregnane-20-one, 3 beta-hydroxy-5 beta-17 (alpha H)-etianic acid methyl ester, androst-4-ene-3,17-dione, and testosterone. About 20 metabolites have been isolated and purified by silicagel chromatography and semi-preparative reverse-phase HPLC. These metabolites have been fully characterized by 1H, 13C NMR and mass spectrometry. All the identified metabolites were hydroxylated at some distinct positions, such as 6 beta-, 7 alpha-, 9 alpha-, 14 alpha-, 15 beta-, or dihydroxylated at 6 beta,14 alpha-,7 alpha,14 alpha-, 9 alpha,14 alpha-, 14 alpha,15 alpha-, 14 alpha,15 beta-positions; nine of these metabolites have not been reported previously. The relationship between the structural features of the investigated steroids and the site-specific hydroxylation has been delineated, and progesterone was found to be the best substrate for the production of 14 alpha-hydroxylated derivative, using T. piriforme.

Studies on the 14 alpha-hydroxylation of progesterone in Mucor piriformis

Cell-free extracts with high 14 alpha-hydroxylase activity were prepared from induced vegetative cell cultures of Mucor piriformis by grinding in potassium phosphate buffer (0.05 M, pH 8.0) containing glucose (0.25 M), KCl (1 mM), glutathione (1.0 mM) and glycerol (10%). Although the ideal pH for preparing the cell-free extract from vegetative cells was 8.0, the pH optimum of the hydroxylase was found to be 7.6. Microsomes (2.0 mg) prepared from the crude cell-free extract hydroxylated progesterone to 14 alpha-hydroxyprogesterone in approximately 60% yields in 30 min in the presence of NADPH and O2. Microsomes prepared from the uninduced cells did not contain any 14 alpha-hydroxylase activity. The hydroxylase activity was inhibited to a significant extent by CO and p-chloromercuribenzoate whereas moderate inhibition was noticed in the presence of SKF-525A, metyrapone and N-methylmaleimide indicating the possible involvement of the cytochrome P-450 system in the reaction. The membrane bound hydroxylase was solubilized using Triton X-100 and the solubilized fraction contained nearly 35% of the original hydroxylase activity.

The identification of 14 alpha,17 beta-dihydroxyandrost-4-en-3-one monohydrate and 14 alpha,17 beta-dihydroxyandrosta-1,4-dien-3-one monohydrate, metabolites of androstenedione in Mucor piriformis

The microorganism Mucor piriformis transforms androst-4-ene-3,17-dione into a major and several minor metabolites. X-ray crystallographic analysis of two of these metabolites was undertaken to determine unambiguously their composition and chirality. Crystals belong to the orthorhombic space-group P2(1)2(1)2(1), with a = 7.199(4) A and a = 6.023(3) A, b = 11.719(3) A and b = 13.455(4) A, c = 20.409(3) A and c = 20.702(4) A for the two title compounds, respectively. The structures have been refined to final R values of 0.060 and 0.040, respectively.

Biotransformation of polycyclic aromatic compounds by fungi

Incubations of several polycyclic aromatic hydrocarbons (PAHs) and heteroaromatic compounds with a series of common micro-organisms have been performed. The PAHs were not metabolized by any of the fungi studied. The sulphur-containing heterocyclic aromatic compounds dibenzothiophene, thioxanthone and thiochromanone were oxidized at sulphur by C. elegans. Other fungi are capable of oxidation at the sulphur atom of dibenzothiophene and thioxanthone. C-1 and C-3 methyl substituted thioxanthones are hydroxylated at the methyl group by C. elegans.

Microbial 7alpha-hydroxylation of 3-ketobisnorcholenol

The transformation of 22-hydroxy-23,24-bisnorchol-4-en-3-one to 7alpha-22-dihydroxy-23,24-bisnorchol-4-en-3-one by Botryodiploida theobromae, Lasiodiplodia theobromae, and various Botryosphaeria strains is described. Factors affecting the reaction were incubation temperature, sonication of the substrate, and addition of 2,2'-dipyridyl, extra carbohydrate, and Amberlite XAD-7. The enzyme responsible for the reaction appeared to be very specific and was not characteristic of all members of the genera listed above.

Reduction of the 20-carbonyl group of C-21 steroids by spores of Fusarium solani and other microorganisms. I. Side-chain degradation, epoxide cleavage, and substrate specificity

The spores of Fusarium solani reduced the C(2)-carbonyl group, 1-dehydrogenated ring "A" and cleaved the side chain of 16alpha, 17alpha-oxidopregn-4-ene-3, 20-dione (16alpha, 17alpha-oxidoprogesterone)(I) to give the following products: 20alpha-hydroxy-16alpha, 17alpha-oxidopregn-4-en-3-one(II); 20alpha-hydroxy-16alpha, 17alpha-oxidopregna-1, 4-dien-3-one(III); 16alpha-hydroxy-17a-oxa-androsta-1, 4-diene-3, 17-dione (16alpha-hydroxy-1-dehydrotestololactone)(IV); and 16alpha, 17beta-dihydroxy-androsta-1, 4-dien-3-one (16alpha-hydroxy-1-dehydrotestosterone)(V). When II was used as a substrate, it was metabolized into III, IV, and V at a slower rate than I. Furthermore, 16alpha-hydroxy-androst-4-ene-3, 17-dione (16alpha-hydroxyandrostenedione)(X) was transformed into IV and V. Pregn-4-ene-3, 20-dione (progesterone)(XII) was transformed into androsta-1, 4-diene-3, 17-dione (androstadienedione)(VIII) and 17a-oxa-androsta-1, 4-diene-3, 17-dione (1-dehydrotestololactone)(IX), while 17alpha-hydroxy-pregn-4-ene-3, 20-dione (17alpha-hydroxyprogesterone)(VI) was converted into its 1-dehydro analogue (VII) without accumulation of any 20-dihydro compounds. Substrate specificity in the 20-reductase system of F. solani, Cylindrocarpon radicicola, Septomyxa affinis, Bacillus lentus, and three strains of B. sphaericus are demonstrated. The 20-reductase is active only on steroids having the 16alpha, 17alpha-oxido, and Delta(4)-3-keto functions. Evidence of competition between side-chain degrading enzymes and the 20-reductase for the steroid molecule and evidence of side-chain degradation followed by epoxide cleavage (and not the reverse) are presented. A mechanism for the epoxide opening by nongerminating spores of F. solani is postulated.