Purification and properties of 16 alpha-hydroxyprogesterone dehydroxylase from Eubacterium sp. strain 144

Eubacterium sp. strain 144 converts 16 alpha-hydroxyprogesterone to 17-isoprogesterone. The first step of this reaction is catalyzed by 16 alpha-hydroxyprogesterone dehydroxylase (16 alpha-dehydroxylase). This enzyme was purified 40-70-fold and characterized. 16 alpha-Dehydroxylase was found to be active in two molecular weight forms of Mr 181 000 and 326 000. A subunit relative molecular weight of 42 400 was determined by sodium dodecyl sulfate gel electrophoresis of the purified enzyme. Although active with both 16 alpha-hydroxyprogesterone and 16 alpha-hydroxypregnenolone, the affinity of 16 alpha-dehydroxylase for the latter steroid was twice that of the former based on the apparent Km values. Evidence of possible substrate inhibition at high concentrations was seen with 16 alpha-hydroxypregnenolone. 16-Ketoprogesterone was found to be a competitive inhibitor of 16 alpha-dehydroxylase with respect to both steroid substrates. Although generally unaffected by low concentrations of non-ionic detergents, 16 alpha-dehydroxylase activity was stimulated 3-7-fold by sodium dodecyl sulfate and inhibited strongly by cetyltrimethylammonium bromide.