title: Role of microsomal steroid hydroxylases in Δ7-steroid biosynthesis.
abstract: CYP17 (steroid 17α-hydroxylase/17,20-lyase) is a key enzyme in steroid hormone biosynthesis. It catalyzes two independent reactions at the same active center and has a unique ability to differentiate Δ(4)-steroids and Δ(5)-steroids in the 17,20-lyase reaction. The present work presents a complex experimental analysis of the role of CYP17 in the metabolism of 7-dehydrosteroids. The data indicate the existence of a possible alternative pathway of steroid hormone biosynthesis using 7-dehydrosteroids. The major reaction products of CYP17 catalyzed hydroxylation of 7-dehydropregnenolone have been identified. Catalytic activity of CYP17 from different species with 7-dehydropregnenolone has been estimated. It is shown that CYP21 cannot use Δ(5)-Δ(7) steroids as a substrate.
authors.affiliation: Institute of Bioorganic Chemistry, National Academy of Sciences of Belarus, Minsk, Belarus. sushko-tatjana@rambler.ru
authors.forename: T A
authors.initials: TA
authors.lastname: Sushko
authors.forename: A A
authors.initials: AA
authors.lastname: Gilep
authors.forename: A V
authors.initials: AV
authors.lastname: Yantsevich
authors.forename: S A
authors.initials: SA
authors.lastname: Usanov
mesh_terms: D055162:Biocatalysis; D006801:Humans; D007700:Kinetics; D008861:Microsomes / Q000737:chemistry / Q000201:enzymology* / Q000378:metabolism; D013254:Steroid 17-alpha-Hydroxylase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D013255:Steroid 21-Hydroxylase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D013256:Steroids / Q000096:biosynthesis* / Q000737:chemistry; D013379:Substrate Specificity
chemical_list: D013256:Steroids; C531510:CYP21A2 protein, human; D013255:Steroid 21-Hydroxylase; C501892:CYP17A1 protein, human; D013254:Steroid 17-alpha-Hydroxylase