Purification and characterization of 7α-hydroxy-4-cholesten-3-one 12α-hydroxylase.

The isoform of cytochrome P450 that catalyzes the 12α-hydroxylation of 7α-hydroxy-4-cholesten-3-one, an intermediate in the conversion of cholesterol to cholic acid, was purified to homogeneity from rabbit liver microsomes. The extent of purification in the various steps was judged by an assay involving high performance liquid chromatography. The purified enzyme showed a single band on SDS-polyacrylamide gel electrophoresis (M r =50,000)