摘要：

1. 1. A3-oxo-5 β-steroid Δ 4-dehydrogenase (EC 1.3.99.5) has been demonstrated in a strain of Clostridium paraputrificum. The enzyme had a pH optimum of 7–8, was only active on 5β steroids and was inactive on steroids with a 3,7-dioxo-5β structure. The presence of a 12-oxo group or the configuration at C-17 had no effect on enzyme activity. 2. 2. A3-oxo-5 β-steroid Δ 1-dehydrogenase (EC 1.3.99.4) was also produced by the same strain. It had a pH optimum between 8 and 9, and was only active on 5β steroids. 3. 3. Both enzymes were able to use the artificial electron acceptor phenazine methosulphate as well as O 2 as the terminal electron acceptor.

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