Transformation of 3-hydroxy-steroids by Fusarium moniliforme 7 alpha-hydroxylase

Transformation of physiologically important 3-hydroxy-steroids by the DHEA- induced 7 alpha-hydroxylase of F. moniliforme was investigated. Whereas DHE A was almost totally 7 alpha-hydroxylated, PREG, EPIA and ESTR were only pa rtially converted into their 7 alpha-hydroxylated derivatives because hydro xylation at other undetermined positions as well as reduction of ketone at C17 or C20 into hydroxyl also occurred. Cholesterol was not transformed by the enzyme. Kinetic parameters of the 7 alpha-hydroxylation for these subst rates were determined and confirmed that DHEA was the best substrate of the 7 alpha-hydroxylase. Inhibition studies of DHEA 7 alpha-hydroxylation by t he other 3-hydroxy-steroids were also carried out and proved that DHEA, PRE G, EPIA and ESTR shared the same active site of the enzyme. Induction effec ts of these steroids were compared, and DHEA appeared to be the best induce r of the 7 alpha-hydroxylase of F, moniliforme. (C) 1999 Elsevier Science L td. All rights reserved.