Mode of action of steroid desmolase and reductases synthesized by Clostridium "scindens" (formerly Clostridium strain 19).

A recently isolated hitherto unknown Clostridium from human feces, designated Clostridium "scindens" (formerly strain 19), synthesizes at least two enzymes active on the side-chain of the steroid molecule and two enzymes active on the hydroxyl groups of the 7-position of bile acids. Steroid desmolase, responsible for side-chain cleavage of corticoids, and 20 alpha-hydroxysteroid dehydrogenase have not been detected in any other bacterial species of the resident colonic flora. Steroid desmolase is Eh-dependent (optimum ca.

Reduction of 17-keto steroids by anaerobic microorganisms isolated from human fecal flora.

The 17-keto function of phenolic steroids is reduced by the following intestinal bacteria: Eubacterium lentum, Clostridium paraputrificum, Clostridium J-1 and Clostridium innocuum. The 17-keto group of androstenedione is reduced solely by Bacteroides fragilis.