Biotransformation of 16 alpha-hydroxyprogesterone by Eubacterium sp. 144: non-enzymatic addition of L-cysteine to delta 16-progesterone.

Eubacterium sp. 144 dehydroxylated 16 alpha-hydroxy-progesterone; however, the expected intermediate, delta 16-progesterone, did not accumulate to significant concentrations in the culture medium. Moreover, the final end product of this biotransformation, 17 alpha-progesterone, was produced at a very slow rate. It was discovered that, under our culture conditions, delta 16-progesterone reacted chemically with L-cysteine to form a highly water-soluble derivative. The ability of delta 16-progesterone to react with L-cysteine in culture media was considerably reduced when L-cysteine was autoclaved in the presence of complex medium components. delta 16-Progesterone also reacted chemically with D-cysteine, L-homocysteine, glutathione, and 2-mercaptoethylamine. The reaction was favored by alkaline pH (greater than or equal to pH 8.0) and required both an unhindered thiol group and a proximal amino group on the mercapto compound. Chromatography of the putative delta 16-progesterone L-[U-14C]-cysteine reaction product by HPLC showed a single UV-absorbing, radioactive peak (RT 4.31 min).