Amino-terminal sequence analysis of six cytochrome P-450 isozymes purified by monoclonal antibody directed immunopurification.

Six hepatic microsomal cytochromes P-450 were isolated from 3-methylcholanthrene induced animals by immunopurification using two monoclonal antibodies. Two forms of cytochromes P-450 (MW 56K and 57K) were from Sprague-Dawley rats, two from C57BL/6 mice (56K and 57K), one form from DBA/2 mice (56K) and one form from guinea pigs (53K). NH2-terminal sequences of the first ten amino acids of these cytochromes P-450 were determined by automated Edman degradation. The 56K polypeptides from rats, C57BL/6 mice, and DBA/2 mice were shown to have identical NH2-terminal sequences. The 57K polypeptides from rats and C57BL/6 mice are homologous to each other but exhibit no homology to 56K polypeptides. The 53K polypeptide from guinea pigs has a unique NH2-terminal sequence with no apparent homology to the other five cytochromes P-450.