Oxidation of 5 beta-cholestane-3 alpha,7 alpha, 12 alpha-triol into 3 alpha,7 alpha,12 alpha-trihydroxy-5 beta-cholestanoic acid by cytochrome P-450(26) from rabbit liver mitochondria.
The mitochondrial cytochrome P-450(26), previously shown to catalyze 26-hydroxylation of 5 beta-cholestane-3 alpha, 7 alpha, 12 alpha-triol, was found to convert this substrate also into 3 alpha,7 alpha,12 alpha-trihydroxy-5 beta-cholestanoic acid. The formation of 3 alpha,7 alpha,12 alpha-trihydroxy-5 beta-cholestanoic acid increased with increasing incubation time and enzyme concentration. Addition of NAD+ to the incubation mixture did not increase the formation of the acid. Incubation with 5 beta-cholestane-3 alpha,7 alpha,12 alpha,26-tetrol, cytochrome P-450(26), ferredoxin, ferredoxin reductase and NADPH resulted in one major product, 3 alpha,7 alpha, 12 alpha-trihydroxy-5 beta-cholestanoic acid. The cytochrome P-450 required both ferredoxin, ferredoxin reductase and NADPH for activity. NADPH could not be replaced by NAD+ or NADP+.
Dahlbäck
H
H
Department of Pharmaceutical Biochemistry, University of Uppsala, Sweden.
Holmberg
I
I
D000818:Animals; D053493:Cholestanetriol 26-Monooxygenase; D002777:Cholestanols / Q000378:metabolism*; D002793:Cholic Acids / Q000096:biosynthesis*; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D007536:Isomerism; D007700:Kinetics; D008930:Mitochondria, Liver / Q000201:enzymology*; D011817:Rabbits; D013250:Steroid Hydroxylases / Q000378:metabolism*
D002777:Cholestanols; D002793:Cholic Acids; C009561:3,7,12-trihydroxycoprostane; C003681:3,7,12-trihydroxycoprostanic acid; D003577:Cytochrome P-450 Enzyme System; D013250:Steroid Hydroxylases; D053493:Cholestanetriol 26-Monooxygenase