The stereochemistry of hydrogen elimination from C-7 in cholesterol and ergosterol biosynthesis.
The synthesis of [7alpha-(3)H]lanosterol is described. It is shown that in the conversion of [7alpha-(3)H,26,27-(14)C(2)]lanosterol into cholesterol by a rat liver system, it is the 7beta-hydrogen atom that is predominantly removed. On the other hand, the conversion of doubly labelled lanosterol into ergosterol by whole yeast cells results in the loss of the 7alpha-hydrogen atom. These results therefore suggest that the C-7 hydrogen atoms with opposite stereochemistry are labilized by the rat liver and the yeast Delta(8)-Delta(7) steroid isomerases.
D000818:Animals; D002247:Carbon Isotopes; D002784:Cholesterol / Q000096:biosynthesis*; D066298:In Vitro Techniques; D008099:Liver / Q000378:metabolism; D051381:Rats; D012440:Saccharomyces / Q000378:metabolism; D013237:Stereoisomerism; D014316:Tritium; D014807:Vitamin D / Q000096:biosynthesis*
D002247:Carbon Isotopes; D014316:Tritium; D014807:Vitamin D; D002784:Cholesterol