Mode of action of steroid desmolase and reductases synthesized by Clostridium "scindens" (formerly Clostridium strain 19).
1984; Elsevier BV; Volume: 25; Issue: 10 Linguagem: Inglês
10.1016/s0022-2275(20)37722-1
ISSN1539-7262
AutoresJ. Winter, George N. Morris, S. O'Rourke-Locascio, V. Bokkenheuser, E.H. Mosbach, Bertram I. Cohen, Phillip B. Hylemon,
Tópico(s)Steroid Chemistry and Biochemistry
ResumoA recently isolated hitherto unknown Clostridium from human feces, designated Clostridium "scindens" (formerly strain 19), synthesizes at least two enzymes active on the sidechain of the steroid molecule and two enzymes active on the hydroxyl groups of the 7-position of bile acids.Steroid desmolase, responsible for sidechain cleavage of corticoids, and 2Oa-hydroxysteroid dehydrogenase have not been detected in any other bacterial species of the resident colonic flora.Steroid desmolase is Ehdependent (optimum ca.-130 mV), requires a hydroxy group at C-17, and preferably an a-keto1 group in the side-chain; an a-hydroxy group at C-20 reduces and a 0hydroxy group at C-20 prevents side-chain cleavage.With suitable substrates, the yield of C-19 steroids is proportional to the bacterial multiplication rate.20a-Hydroxysteroid dehydrogenase (20a-HSDH) is also Ehdependent (optimum ca.-300 mV) and reduces the C-20 keto function to an a-hydroxy group, regardless of the presence or absence of a hydroxy group at C-17. 7a-Dehydroxylase metabolizes cholic and chenodeoxycholic acid, while 7@-hydroxysteroid dehydrogenase acts upon ursodeoxycholic acid.The latter two enzymes are not specific for C. scindens.-
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