Oxidation of 3-oxygenated delta 4 and delta 5 - C27 steroids by soybean lipoxygenase and rat liver microsomes.
The formation of dioxygenated metabolites of cholesterol, epicholesterol (5-cholesten-3 alpha-ol) 4-cholesten-3 beta-ol, 4-cholesten-3 alpha-one and 4-stigmasten-3-one was studied after incubations with soybean lipoxygenase and linoleic acid. From cholesterol and epicholesterol were formed the 7 alpha-hydroxy, 7 beta-hydroxy-, 7 beta-hydroperoxy-, 7-oxo and 5,6-epoxy-derivatives as well as 6 beta-hydroxy-4-cholesten-3-one. All delta 4-steroids were hydroxylated in the 6 alpha- and 6 beta-positions. The ratios between the yields of 6 beta- and 6 alpha-hydroxylated metabolites varied between 3:1 and 2:1. Incubations with 4-cholesten-3 alpha-ol and 4-cholesten-3 beta-ol also afforded the 4,5-epoxides of these steroids. The ratios between the yields of the 4 beta, 5 beta- and 4 alpha, 5 alpha-epoxides were ca. 4:1 for 4-cholesten 3 beta-ol and ca. 3:2 for 4-cholesten-3 alpha-ol. With iron-supplemented microsomes from rat liver, the compounds formed were qualitatively and quantitatively the same as with soybean lipoxygenase, whereas with 18,000 X g rat liver supernatant fractions the yields of all products formed--except 7 alpha-hydroxycholesterol and 6 beta-hydroxy-4-cholesten-3-one--were markedly decreased. The results indicate the presence of a rat liver microsomal 6 beta-hydroxylase which can use 4-cholesten-3-one as a substrate and extend previous findings of similarities between soybean lipoxygenase and a nonspecific lipoxygenase in rat liver microsomes.
D000818:Animals; D002783:Cholestenones / Q000378:metabolism; D002784:Cholesterol / Q000031:analogs & derivatives / Q000378:metabolism; D002792:Cholestyramine Resin / Q000494:pharmacology; D007501:Iron / Q000494:pharmacology; D007536:Isomerism; D008084:Lipoxygenase / Q000378:metabolism*; D008862:Microsomes, Liver / Q000187:drug effects / Q000378:metabolism*; D010084:Oxidation-Reduction; D051381:Rats; D013237:Stereoisomerism; D013265:Stigmasterol / Q000031:analogs & derivatives / Q000378:metabolism
D002783:Cholestenones; D002792:Cholestyramine Resin; D002784:Cholesterol; D013265:Stigmasterol; D007501:Iron; D008084:Lipoxygenase