Open AccessMicrobial Transformation of Cholesterol into Coprostanol
Author(s) -
Björkhem Ingemar,
Wrange Örjan,
Gustafsson JanÅke
Publication year - 1973
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1973.tb02968.x
Subject(s) - pregnenolone , double bond , steroid , dehydroepiandrosterone , chemistry , enzyme , reductase , cholesterol , biochemistry , organic chemistry , hormone , androgen
The conversion of 4‐cholesten‐3‐one into 5β‐cholestan‐3‐one (coprostanone) by microorganisms in caecal contents from rats has been studied. The enzyme activity was present in the soluble part of a homogenate obtained by freeze‐pressing of caecal contents of rats. The major part of the activity could be precipitated between 25 and 50% saturation with ammonium sulphate. The 3‐oxo‐Δ 4 ‐steroid 5β‐reductase activity required NADH as cofactor and was inhibited by p‐chloromercuribenzoate. The enzyme preparation also catalyzed the reduction of the Δ 4 ‐double bond in progesterone and testosterone but did not catalyze reduction of the Δ 5 ‐double bond in cholesterol, pregnenolone or dehydroepiandrosterone. The rate of reduction of the Δ 4 ‐double bond in progesterone was more than twice as fast as the rate of reduction of the Δ 4 ‐double bond in 4‐cholesten‐3‐one. The mechanism of reduction of Δ 4 ‐double bonds in 3‐oxo‐Δ 4 ‐steroids by the microbial 3‐oxo‐Δ 4 ‐steroid 5β‐reductase was found to involve transfer of hydrogen from the 4 B ‐position of NADH to the 5β‐position of the steroid.