Aringer L
Lipids. 1980 Aug;15(8):563-71. doi: 10.1007/BF02534180.
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.
在与大豆脂氧合酶和亚油酸共同孵育后，对胆固醇的双加氧代谢产物表胆固醇（5-胆甾烯-3α-醇）、4-胆甾烯-3β-醇、4-胆甾烯-3α-酮和4-豆甾烯-3-酮的形成进行了研究。胆固醇和表胆固醇形成了7α-羟基、7β-羟基、7β-氢过氧基、7-氧代和5,6-环氧衍生物以及6β-羟基-4-胆甾烯-3-酮。所有δ4-类固醇在6α和6β位均被羟基化。6β-和6α-羟基化代谢产物的产率之比在3:1至2:1之间变化。用4-胆甾烯-3α-醇和4-胆甾烯-3β-醇孵育也得到了这些类固醇的4,5-环氧化物。4β,5β-和4α,5α-环氧化物的产率之比，对于4-胆甾烯-3β-醇约为4:1，对于4-胆甾烯-3α-醇约为3:2。用大鼠肝脏补充铁的微粒体时，形成的化合物在定性和定量上与用大豆脂氧合酶时相同，而用18,000×g大鼠肝脏上清液组分时，除7α-羟基胆固醇和6β-羟基-4-胆甾烯-3-酮外，所有形成产物的产率均显著降低。结果表明大鼠肝脏微粒体中存在一种6β-羟化酶，其可以使用4-胆甾烯-3-酮作为底物，并扩展了先前关于大豆脂氧合酶与大鼠肝脏微粒体中一种非特异性脂氧合酶之间相似性的发现。
