STEROIDS AS SUBSTRATES FOR CHOLESTEROL - OXYGEN OXIDOREDUCTASE, WITH SPECIAL REFERENCE TO 3-BETA-HYDROXY BILE-ACIDS

Cholesterol: oxygen oxidoreductase [EC 1.1.3.6] from Brevibacterium sterolicum (ATCC 21387) was found to catalyze the oxidation of steroids such as sterols, steroid hormones, and bile acids having a free C-3β hydroxyl group. However, the enzyme was inactive towards estradiol and estriol and had a weak activity towards steroids with functional groups adjacent to the 3β- group on the steroid nucleus.Variation in the length of the side chain of 3β steroids had no marked effect on the activity.3β-Hydroxy bile acids with δ4 or δ5 were oxidized to almost the same extent as cholesterol. In contrast, 3β-hydroxy bile acids without δ4 or δ5 were oxidized only to the extent of 1.4-2.1%.3β-Hydroxychol-4 or 5-enoic acid was oxidized in the same way as cholesterol.This enzyme is useful as a simple tool for identification of 3β-hydroxy groups of bile acids. © 1979 By The Journal Of Biochemistry.