Mechanism of peroxisomal 24-hydroxylation of 3 alpha,7 alpha,12 alpha-trihydroxy-5 beta-cholestanoic acid in rat liver.

We recently showed that the peroxisomal fraction of rat liver has a high capacity to catalyze conversion of 3 alpha,7 alpha,12 alpha-trihydroxy-5 beta-cholestanoic acid into cholic acid and that 3 alpha,7 alpha,12 alpha,24-tetrahydroxy-5 beta-cholestanoic acid is an intermediate in this conversion. With use of 2H2O and 18O2, evidence is presented here that the formation of 3 alpha,7 alpha,12 alpha,24-tetrahydroxy-5 beta-cholestanoic acid involves intermediary formation of a delta 24-unsaturate intermediate followed by hydration.