title: Purification and characterization of a previously unreported form of cytochrome P-448 from the liver of 3-methylcholanthrene-pretreated rats.
abstract: At least four hepatic isoenzymes of cytochrome P-450 were purified and characterized from rats treated with 3-methylcholanthrene. A monoclonal antibody developed against one of the forms (designated cytochrome P-450 MC-B) and polyclonal antibodies against others were used to demonstrate that form MC-B is immunologically distinct from other methylcholanthrene-inducible forms. Limited N-terminal amino acid sequencing showed that cytochrome P-450 MC-B has a primary structure that differs from the N-terminal sequences of other established rat isoenzymes. Cytochrome P-450 MC-B has a minimum Mr of 53,000, a CO-reduced spectral maximum at 448 nm, a Soret maximum of 417 nm in the absolute oxidized spectrum and a pattern of substrate preferences that differs from those of the other methylcholanthrene-induced forms. The other forms (MC-A, MC-C and MC-D) share characteristics with isoenzymes previously reported by other investigators.
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D019388:Cytochrome P-450 CYP1A2; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism; D003580:Cytochromes / Q000276:immunology / Q000302:isolation & purification / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D007527:Isoenzymes / Q000378:metabolism; D008099:Liver / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D008748:Methylcholanthrene / Q000494:pharmacology*; D051381:Rats; D013053:Spectrophotometry; D013379:Substrate Specificity
chemical_list: D003580:Cytochromes; D007527:Isoenzymes; D008748:Methylcholanthrene; D003577:Cytochrome P-450 Enzyme System; C017170:Cyp1a2 protein, rat; D019388:Cytochrome P-450 CYP1A2