PURIFICATION AND CHARACTERIZATION OF 2 NEW CYTOCHROME-P-450 RELATED TO CYP2C SUBFAMILY FROM RABBIT SMALL-INTESTINE MICROSOMES

Two forms of cytochrome P-450, designated P-450id and P-450ie, were pu rified to specific contents of 14.3 and 15.0 nmol of P-450/mg of prote in, respectively, from small intestine mucosa microsomes of rabbits. P -450id and P-450ie showed apparent molecular weights of 50 and 49 kDa, respectively, on SDS-PAGE. Both P-450s catalyzed N-demethylation of n itrosodimethylamine. The NH2-terminal amino acid sequence (first 19 re sidues) of P-450id exhibited 74-90% identity with those of six members of the rabbit P-450 2C subfamily, except for P-450 2C3. similarly, th e NH2-terminal sequence (first 22 residues) of P-450ie showed 73-86% i dentity with those of the same members of the rabbit P-450 2C subfamil y. The peptide mapping patterns of the two P-450s were quite different from each other. In addition, P-450id did not cross-react with the gu inea-pig antibodies against P-450ie. The results indicate that rabbit small intestine mucosa contain two new distinct forms of P-450s, both of which may be classified into the 2C subfamily.