Stereoisomeric inversion of (25R)- and (25S)-3 alpha,7 alpha,12 alpha-trihydroxy-5 beta-cholestanoic acids in rat liver peroxisome.

The stereoisomeric inversion of (25R)- and (25S)-3 alpha,7 alpha,12 alpha-trihydroxy-5 beta-cholestanoic acid (THCA) in rat liver peroxisome was studied. After incubation of an isomer of THCA-CoA thioester with a peroxisomal fraction, 5 beta-cholestanoic acids were extracted and optical antipodes were separated and determined by LC/APCI-MS. The transformation of (24E)-3alpha,7 alpha,12 alpha-trihydroxy-5 beta-cholest-24-en-26-oic acid (delta 24-THCA) formed by acyl-CoA oxidase was also analyzed by GC/NICI-MS. Rapid enzymatic epimerization from either direction was observed prior to biotransformation into (24E)-delta 24-THCA.