title: Characterization of a corticosteroid 21-dehydroxylase from the intestinal anaerobic bacterium, Eubacterium lentum.
abstract: An oxygen-sensitive corticosteroid 21-dehydroxylase has been characterized in cell extracts of Eubacterium lentum. The enzyme was highly specific for corticosteroids containing and alpha-ketol structure and required FMNH2 or reduced benzyl viologen for activity. The enzyme used deoxycorticosterone, deoxycortisol, dehydrocorticosterone, and corticosterone as substrates. Substrate saturation kinetics using [3H]corticosterone yielded an apparent Km of 7.35 microM and a Vmax of 15.4 nmol (11 beta-[3H]hydroxyprogesterone) formed per hr x mg protein-1. 21-Dehydroxylase activity was inhibited by both water-soluble and lipophilic metal ion chelators. NADH: flavin oxidoreductase and 21-dehydroxylase activities were separated by anaerobic DEAE-cellulose and Sepharose 6B chromatography. 21-Dehydroxylase had a relative weight of 582,000 as determined by Sepharose 6B chromatography. There was a 7-fold increase in the rate of 21-dehydroxylation of [3H]deoxycorticosterone in whole cell suspensions of E. lentum sparged with H2 as compared to argon gas.
mesh_terms: D000693:Anaerobiosis; D005051:Eubacterium / Q000201:enzymology* / Q000254:growth & development; D006801:Humans; D007422:Intestines / Q000382:microbiology; D007700:Kinetics; D013255:Steroid 21-Hydroxylase / Q000302:isolation & purification / Q000378:metabolism*; D013250:Steroid Hydroxylases / Q000378:metabolism*; D013379:Substrate Specificity
chemical_list: D013250:Steroid Hydroxylases; D013255:Steroid 21-Hydroxylase