TRANSFORMATION OF 4-ANDROSTEN-3,17-DIONE BY GROWING CULTURES AND CELL-EXTRACTS OF CLOSTRIDIUM - PARAPUTRIFICUM

Growing cultures of Clostridium paraputrificum transformed 4-androsten-3,17-dione to 3α-hydroxy-5β-androstan-17-one in a sequential manner with 5β-androstan-3,17-dione as an intermediate. The addition of 1.5 mM menadione to log-phase cultures which had formed 5{circled dash}androstan-3,17-dione resulted in a partial reoxidation of this steroid to 4-androsten-3,17-dione. However, this treatment also resulted in transient inhibition of culture growth. Resumption of growth was accompanied by complete reduction of 4-androsten-3,17-dione to 5β-androstan-3,17-dione. Cell extracts of C. paraputrificum were capable of carrying out these reductive transformations in the absence of added cofactors. However, Sephadex G-25 treated extracts required NADH or NADPH for these reactions. A flavin nucleotide, either FAD (plus NADH or NADPH) or FMN (plus NADH) was highly stimulatory for 4-androsten-3,17-dione reduction to 5β-androstan-3,17-dione. NADH was the preferred reduced pyridine nucleotide for reduction of the C4-C5 double bond, while time-course measurements suggested that NADPH was the preferred donor for reduction of the 3-keto group. © 1979.