Purification of a cytochrome P450 isozyme belonging to a subfamily of P450 IIB from liver microsomes of guinea pigs.

An isozyme of cytochrome P450 was purified from liver microsomes of guinea pigs by HPLC with anion-exchange and hydroxylapatite columns. The isozyme showed a single band of 52 kdalton on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Oxidation activities of the final preparation towards p-nitroanisole, aniline and d-benzphetamine were 1.3 to 15.4-fold comparing with those of microsomal fraction. This isozyme was also concerned with oxidation of delta 9-tetrahydrocannabinol (THC) to 8 alpha-hydroxy- (8 alpha-OH-), 2'-OH- and 3'-OH-delta 9-THCs. The N-terminal region of the isozyme was considerably hydrophobic, and 13 of the first 20 amino acid residues was leucine. Since this first 20 amino acid sequence is 80% homologous with that of cytochrome P450 LM2 purified from rabbit liver microsomes, this isozyme can be categorized to a subfamily of P450 IIB.