Efficient hydroxylation of functionalized steroids by Colletotrichum lini ST-1

Cofactor-dependence alteration of 7β-hydroxysteroid dehydrogenase: Enhancing one-pot synthesis efficiency of chenodeoxycholic acid to ursodeoxycholic acid through cofactor self-recycling

NAD+-dependent 7α-hydroxysteroid dehydrogenase (7α-HSDH) and NADPH-dependent 7β-hydroxysteroid dehydrogenase (7β-HSDH) are involved in the biosynthesis of chenodeoxycholic acid (CDCA) to ursodeoxycholic acid (UDCA). To realize the one-pot synthesis of CDCA to UDCA through NAD+-NADH cycling, we aimed to improve the binding ability of Hyphomicrobium sp. 7β-HSDH to NADH. The 7β-HSDH structure was modeled and some potential residues to improve NADH affinity near conserved cofactor binding regions were screened, including Ala22, Gln23, Asn24, Asp44, Leu45, and Asn46. The dominant mutant A22T/Q23E/L45A/N46E significantly enhanced the binding affinity for NADH, resulting in a 44.9-fold increase in its kcat/Km value. It increased enzymatic activity by 65.2-fold and catalyzed the synthesis of UDCA at a yield of 77.6 % with 5 g/L 7K-LCA and 12.5 mM NADH. Molecular dynamics simulations indicated increased interactions of mutated 7β-HSDH and the ligand NADH by their spatially reduced binding distance and reaction energy. The modified cofactor-dependence of 7β-HSDH realized efficient one-pot synthesis of CDCA to UDCA through strengthening cofactor-recycling and reducing the use of cofactor, achieving 90.1 % UDCA yield and 54.1 g/L/d spatiotemporal yield when coupled with 7α-HSDH with only 0.5 mM NAD+ as coenzyme. This work also supplies a universal cofactor-dependence engineering technique for homologous HSDH enzymes.

Biotransformation of testosterone by the filamentous fungus Penicillium pinophilum

The microbial biotransformation is a robust procedure in developing steroids and fungi are practical tools in this process; therefore, the fungal modification of testosterone by Penicillium pinophilum was investigated. The three prominent metabolites, including 14α-hydroxyandrost-4-en-3,17-dione (II), 14α-hydroxytestosterone (III), and 11α-hydroxytestosterone (IV), were isolated and characterized by chromatographic and spectroscopic methods. The time course profile showed that the content of the metabolites II and III began to decrease after 96 and 24 h, respectively. In comparison, the content of the metabolite IV remained stable after 24 h. In silico studies showed that the probability of binding to the androgen receptor remains high for all three metabolites. However, the probability of binding to the estrogen receptors α and β increased for metabolite IV but decreased for metabolite III. Penicillium pinophilum as a potentially viable biocatalyst could hydroxylate C-11α and C-14α positions and oxidize the C-17β hydroxyl group to 17-ketone in testosterone molecule.

Hydroxylation of Progesterone and Its Derivatives by the Entomopathogenic Strain Isaria farinosa KCh KW1.1

Progesterone biotransformation is worth studying because of the high industrial value of its derivatives. This study investigated the catalytic ability of the entomopathogenic filamentous fungus strain Isaria farinosa KCh KW1.1 to transform progesterone derivatives: 11α-hydroxyprogesterone, 17α-hydroxyprogesterone, 16α,17α-epoxyprogesterone and pregnenolone. In the culture of Isaria farinosa KCh KW1.1, 11α-hydroxyprogesterone was effectively transformed into only one product: 6β,11α-dihydroxyprogesterone. Transformation of 17α-hydroxyprogesterone gave three hydroxy derivatives: 6β,17α-dihydroxyprogesterone, 12β,17α-dihydroxyprogesterone and 6β,12β,17α-trihydroxyprogesterone. Two products: 6β-hydroxy-16α,17α-epoxyprogesterone and 6β,11α-dihydroxy-16α,17α-epoxyprogesterone, were obtained from the 16α,17α-epoxyprogesterone transformation. We isolated two compounds from the biotransformation medium with pregnenolone: 11α-hydroxy-7-oxopregnenolone and 5α,6α-epoxy-3β,11α-dihydroxypregnan-7,20-dione. In this study, we observed only mono- and dihydroxy derivatives of the tested substrates, and the number of obtained products for each biotransformation did not exceed three.

Identification of a fungal cytochrome P450 with steroid two-step ordered selective hydroxylation characteristics in Colletotrichum lini

Microbial hydroxylation reaction has greatly enriched the number of steroids and created many meaningful new compounds. The dihydroxylation of dehydroepiandrosterone (DHEA) by filamentous fungi produces an important product 3β,7α,15α-trihydroxy-5-androstene-17-one (7α,15α-diOH-DHEA), which can be used as a key intermediate for the synthesis of contraceptive drospirenone. The introduction of microbial hydroxylation reaction reduces the traditional chemical synthesis process by 4 steps and greatly improves the productivity and economic efficiency. Colletotrichum lini is an industrial strain producing 7α,15α-diOH-DHEA, but the related cytochrome P450 that plays hydroxylation effect has not yet been discovered. In this work, a combination of quantitative proteomics, qRT-PCR, and functional expression in Pichia pastoris was used to identify highly induced steroid hydroxylase from Colletotrichum lini ST-1. A novel fungal cytochrome P450 monooxygenase CYP68JX was identified. The biotransformation in recombinant yeast confirmed that the cytochrome P450 has steroid C7α and C15α hydroxylase activities. The hydroxylation of DHEA by CYP68JX is an ordered reaction, proceeding from the C7 to the C15 site of the steroidal nucleus. The cloning and identification of the CYP68JX gene provide useful information for deepening the understanding regarding the structural basis of its regional and stereoselectivity.

iTRAQ-based quantitative proteomic analysis of Colletotrichum lini reveals ethanol induced mechanism for enhancing dihydroxylation efficiency of DHEA

Colletotrichum lini is used as an industrial stain for the dihydroxylation of steroid compound dehydroepiandrosterone (DHEA) to biosynthesize 3β,7α,15α-trihydroxy-5-androstene-17-one (7α,15α-diOH-DHEA), a key intermediate of the most popular oral contraceptive "Yasmin". This work aimed to enhance 7α,15α-diOH-DHEA production in C. lini CGMCC 6051 through ethanol induction. With 0.6% (v/v) ethanol induction and 10 g/L DHEA concentration, the 7α,15α-diOH-DHEA molar yield reached 58.8%, which was increased by 67.5% than that of the control. iTRAQ-based quantitative proteomic analysis was applied to explore the probable molecular mechanism of C. lini response to ethanol induction. A total of 50 differential expressed proteins was affected by ethanol induction, and could be related to multiple metabolic pathways. Most of differently expressed proteins were functionally mapped into pathways of transport, steroids metabolism, or redox reaction. Other proteins for energy, transcription and translation, and carbohydrate metabolism might have important roles in the cellular response to ethanol induction. In addition, the levels of cytochrome P450 and NAD(P)H-cytochrome P450 reductase were remarkably higher under ethanol induction, and their functions on DHEA dihydroxylation were first proposed in C. lini. Our results provide critical clues in revealing the dihydroxylation mechanism and are important for efficient microbiological hydroxylation of steroidal compounds in the future. BIOLOGICAL SIGNIFICANCE: iTRAQ strategy was first used to compare the proteomes of ethanol induction during the dihydroxylation reaction by Colletotrichum lini CGMCC 6051. The changes in protein provided a comprehensive overview of DHEA dihydroxylation in C. lini, including the proteins for steroids metabolism, redox reaction, transport, transcription and translation, energy and carbohydrate metabolism. Cytochrome P450, NADPH-cytochrome P450 reductase, and NADH-cytochrome b5 reductase were highlighted due to their outstanding contribution to DHEA dihydroxylation. The results help us understand the molecular mechanism underlying ethanol induction in C. lini and would guide strain engineering to further improve dihydroxylation efficiency.

Biotransformation of progesterone and testosterone enanthate by Circinella muscae

In this study, the biotransformation of progesterone (1) and testosterone enanthate (5) using the whole cells of Circinella muscae was investigated for the first time. Microbial transformation of 1 with C. muscae afforded three known metabolites including 9α-hydroxyprogesterone (2), 14α-hydroxyprogesterone (3) and 6β,14α dihydroxyprogesterone (4) after 6 days of incubation at 26 °C. The biotransformation of 5 with C. muscae yielded a new metabolite; 8β,14α-dihydroxytestosterone (8), in addition to two known metabolites; 6β-hydroxytestosterone (6), and 9α-hydroxytestosterone (7). The structure of the metabolites were established on the basis of spectroscopic data.

Biotransformation of androst-4-ene-3,17-dione by three fungal species Fusarium solani BH1031, Aspergillus awamori MH18 and Mucor circinelloides W12

The microbial transformation of androst-4-ene-3,17-dione (4-AD; I) by three fungal species, involved Fusarium solani BH1031, Aspergillus awamori MH18 and Mucor circinelloides W12, has been studied. The latter two fungi were studied for the first time on biotransformation of 4-AD. The main product obtained by Fusarium solani BH1031 was 17α-oxa-D-homo-androst-1,4-diene-3,17-dione (testolactone; IV), which can be used as an anticancer agent. The main derivative yielded by Aspergillus awamori MH18 was 11α-hydroxyandrost-4-ene-3,17-dione (11α-OH-4-AD; VI), which was an important intermediate to produce Eplerenone. Meanwhile, the microbial transformation of 4-AD by Mucor circinelloides W12 produced three derivatives. Possible metabolic pathway of 4-AD via Fusarium solani BH1031 was proposed. Furthermore, the optimization for the production of 11α-OH-4-AD was carried out and the conversion rate reached to 84.0%. In this process, the dextrin and corn flour showed significant effects by response surface analysis.

An efficient biotransformation of progesterone into 11α-hydroxyprogesterone by Rhizopus microsporus var. oligosporus

Rhizopus microsporus var. oligosporus is a fungus that belongs to the Mucoraceae family that is used for the preparation of some soy-fermented foods. Microbial biotransformation of progesterone by R. microsporus var. oligosporus afforded some monohydroxylated and dihydroxylated metabolites. The main product was purified using chromatographic methods and identified as 11α-hydroxyprogesterone on the basis of its spectroscopic features. Time course studies by high-performance thin-layer chromatography demonstrated that this fungi efficiently hydroxylated progesterone at the 11α-position for 3 days with a yield of 76.48%, but beyond this time, the microorganism transformed 11α-hydroxyprogesterone into dihydroxylated metabolites. 11α-Hydroxyprogesterone is widely used as a precursor in the synthesis of hydrocortisone and other steroidal anti-inflammatory agents.

Fungal biotransformation of diuretic and antihypertensive drug spironolactone with Gibberella fujikuroi, Curvularia lunata, Fusarium lini, and Aspergillus alliaceus

Derivatives of spironolactone (1), a diuretic and antihypertensive drug, were synthesized by using fungal cells for the first time. Ten different fungi were screened for their ability to biotransform 1, four of which were able to produce metabolites 2-8. Gibberella fujikuroi produced canrenone (2), 1-dehydrocanrenone (3), Curvularia lunuta provided compound 2, and 7α-thio-spironolactone (4), Fusarium lini yielded compounds 2, 3, 1β-hydroxycanrenone (5), 1α-hydroxycanrenone (6), 1-dehydro-15α-hydroxycanrenone (7), and 15α-hydroxycanrenone (8), while Aspergillus alliaceus was able to produce all the seven metabolites. Metabolites 5, 6, and 7 were identified as new compounds. Their structures were elucidated by using different spectroscopic techniques. Substrate 1 and its metabolites 2, 3, and 5-8 were also evaluated for α-glucosidase inhibitory activity in vitro. Substrate 1 was found to be strongly active with IC₅₀ = 335 ± 4.3 μM as compared to the standard drug acarbose IC₅₀ = 840 ± 1.73 μM, whereas all of resulting metabolites were found to be inactive.

Screening for strains with 11α-hydroxylase activity for 17α-hydroxy progesterone biotransformation

Various corticosteroids are prepared by using 11α,17α-diOH-progesterone (11α,17α-diOH-PROG) as an important intermediate and raw material. Hence, strains that can improve the yields of 11α,17α-diOH-PROG should be screened. Cunninghamella elegans CICC40250 was singled out from five common 11α hydroxylation strains. The reaction parameters of 11α,17α-diOH-PROG production were also investigated. C. elegans CICC40250 could efficiently catalyze the hydroxylation of 17α-hydroxy progesterone (17α-OH-PROG) at C-11α position. This strain could also effectively convert 11α,17α-diOH-PROG at high substrate concentrations (up to 30g/L). After the coenzyme precursor glucose was added, the rate of 11α,17α-diOH-PROG formation reached 84.2%, which was 11.4% higher than that of the control group. Our study established a simple and feasible mechanism to increase 11α,17α-diOH-PROG production levels. This mechanism involves C. elegans CICC40250 that can be efficiently applied to induce the biotransformation of 17α-OH-PROG with a hydroxylation biocatalytic ability.

Biotransformation of dehydro-epi-androsterone by Aspergillus parasiticus: Metabolic evidences of BVMO activity

The research on the synthesis of steroids and its derivatives is of high interest due to their clinical applications. A particular focus is given to molecules bearing a D-ring lactone like testolactone because of its bioactivity. The Aspergillus genus has been used to perform steroid biotransformations since it offers a toolbox of redox enzymes. In this work, the use of growing cells of Aspergillus parasiticus to study the bioconversion of dehydro-epi-androsterone (DHEA) is described, emphasizing the metabolic steps leading to D-ring lactonization products. It was observed that A. parasiticus is not only capable of transforming bicyclo[3.2.0]hept-2-en-6-one, the standard Baeyer-Villiger monooxygenase (BVMO) substrate, but also yielded testololactone and the homo-lactone 3β-hydroxy-17a-oxa-D-homoandrost-5-en-17-one from DHEA. Moreover, the biocatalyst degraded the lateral chain of cortisone by an oxidative route suggesting the action of a BVMO, thus providing enough metabolic evidences denoting the presence of BVMO activity in A. parasiticus. Furthermore, since excellent biotransformation rates were observed, A. parasiticus is a promising candidate for the production of bioactive lactone-based compounds of steroidal origin in larger scales.