Abstract
Eubacterium sp. strain 144 is an intestinal anaerobic bacterium which catalyzes a two-step biotransformation of 16 α-hydroxy progesterone to 17-isoprogesterone. 16α-Hydroxyprogesterone dehydroxylase (16α-dehydroxylase) catalyzes the first reaction, yielding Δ 16-progesterone. The present study examined properties of the 16α-dehydroxylase in cell extracts of strain 144. The enzyme exhibited a broad pH range (5.8–8.0) without a distinct pH optimum. 16α-Dehydroxylase was active at high (15–30% v/v) methanol concentrations and a distinct optimum occurred at 25% (v/v). The enzyme was less active with ethanol or short-chain glycols and was inhibited by propanol and butanol. Substrates included 16α-hydroxyprogesterone, 16α-hydroxypregnenolone and Δ 16-progesterone; however, the specific activity with the latter steroid was only 15% of that obtained with the 16α-hydroxysteroids. The substrate saturation curve for 16α-hydroxyprogesterone was hyperbolic and a Lineweaver-Burk plot of the data was linear with an apparent K m of 0.56 ± 0.08 mM. 16α-Dehydroxylase was stable at 60°C for 10 min but was inactivated (70%) at 65°C. An M r of 285 000 was estimated for 16α-dehydroxylase by gel permeation HPLC of strain 144 cell extract.
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