Formation of 5 alpha steroids by biotransformation involving the 5 alpha-reductase activity of Penicillium decumbens.

The biotransformation of a series of delta 4-3-ketosteroids by the fungus Penicillium decumbens ATCC 10436 has been investigated. Conversion to the 5 alpha-dihydrosteroid was observed for several substrates of the androstene and pregnene series: the reaction is tolerant of non-polar substituents (Cl and CH3) at C-4 of the substrate, but does not occur in the presence of a 4-hydroxyl group, or with additional unsaturation at the delta 1 or delta 6 positions. A-nor-, B-nor-, 3-deoxy-, and 3,5-cycloandrostanes are not reduced, but 6-methylenetestosterone is converted to a 6-methylene-5 alpha-dihydro derivative. Several biotransformations are reported which involve oxidoreductase activity at C-3 and/or C-17, either concomitant or independent of delta 4 reduction: the substrate specificity of the oxidoreductase processes has been examined and defined by the use of 3 alpha-hydroxy, 3 beta-hydroxy, 3-keto, 17 beta-hydroxy and 17-keto substituted steroids. In this way, the existence in P. decumbens of 3 beta-hydroxy-3-keto and 17 beta-hydroxy-17-keto oxidoreductases has been demonstrated.