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Cholesterol oxidase is a highly demanded enzyme used in medicine, pharmacy, agriculture, chemistry, and biotechnology. It catalyzes oxidation of 3β-hydroxy-5-ene- to 3-keto-4-ene- steroids with the formation of hydrogen peroxide. Here, we expressed 6xHis-tagged mature form of the extracellular cholesterol oxidase (ChO) from the actinobacterium Nocardioides simplex VKM Ac-2033D (55.6 kDa) in Escherichia coli cells. The recombinant enzyme (ChONs) was purified using affinity chromatography. ChONs proved to be functional towards cholesterol, cholestanol, phytosterol, pregnenolone, and dehydroepiandrosterone. Its activity depended on the structure and length of the aliphatic side chain at C17 atom of the steroid nucleus and was lower with pregnenolone and dehydroepiandrosterone. The enzyme was active in a pH range of 5.25÷6.5 with the pH optimum at 6.0. Kinetic assays and storage stability tests demonstrated that the characteristics of ChONs were generally comparable with or superior to those of commercial ChO from Streptomyces hygroscopicus (ChOSh). The results contribute to the knowledge on microbial ChOs and evidence that ChO from N. simplex VKM Ac-2033D is a promising agent for further applications. [ABSTRACT FROM AUTHOR]

A microbial catalysis is an effective tool for steroid structural modifications allowing generating the compounds which may be difficult to obtain by conventional synthetic methods. Selected fungal strains of Ascomycota and Zygomycota divisions (totally, 75) representing different phyla were screened for their activity toward 3β-hydroxypregn-5-ene-20-one (pregnenolone) focusing on the production of 11α-hydroxyprogesterone. Along with the ability to catalyze 7α-, 7β- and 11α-hydroxylation which was revealed for some representatives of Pleosporaceae, Trichocomaceae, Hypocreaceae, Clavicipitaceae, Microascaceae, Cunninghamellaceae, Mucoraceae and Phycomycetaceae families, micromycete strains belonging to Acremonium, Aspergillus, Curvularia, Rhizopus, and Scopulariopsis genera were selected capable of modifying 3β-ol-5-ene- to 3-keto-4-ene moiety, - this reaction being rather uncommon for fungi. The ability to catalyze double hydroxylation of pregnenolone at positions 7β and 11α by some tested micromycetes was revealed for the first time. Sustainable and high-efficient single-stage production of 11α-hydroxyprogesterone (up to 70%) from pregnenolone which was hitherto unreported was reached with the strain of Aspergillus niger VKM F-212 under the optimized conditions. The results demonstrate a highly diverse biocatalytic potential of fungal strains towards pregnenolone, reveal the existence of novel active biocatalysts that can be exploited for the synthesis of high-value hydroxysteroids and expand knowledge on structural modifications of steroid molecules in lower eukaryotes. [ABSTRACT FROM AUTHOR]