Three immunoidentical cytochromes P-450 from liver microsomes of phenobarbital-treated rats.
Three forms of cytochrome P-450 were purified to homogeneity from liver microsomes of Wistar-strain rats treated with phenobarbital. They had minimum mol.wts. of 52 000, 53 000 and 54 000 as determined by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis and are designated as P-450(L), P-450(M) and P-450(H) respectively. They were shown to be immunoidentical by Ouchterlony double-diffusion analysis. Several criteria, such as isoelectric points, substrate specificities and sensitivities to tryptic digestion, however, indicated that these cytochromes are distinct isoenzymes of cytochrome P-450. Whereas P-450(L) was highly active on various substrates, P-450(H) had generally low catalytic activities, except on aminopyrine. The cytochromes purified by immunoaffinity chromatography using anti-P-450(L) showed a marked variation in their distribution depending on the strain and colony of rat. Limited tryptic digestion of P-450(H) gave one tryptic peptide showing the same mobility as P-450(L) by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis and their primary structures were very similar. The result suggests a possibility that such limited proteolysis is involved in the post-translational modification of the cytochrome or its destruction.
D000818:Animals; D003577:Cytochrome P-450 Enzyme System / Q000276:immunology* / Q000302:isolation & purification; D004591:Electrophoresis, Polyacrylamide Gel; D005779:Immunodiffusion; D007527:Isoenzymes / Q000276:immunology* / Q000302:isolation & purification; D008297:Male; D008862:Microsomes, Liver / Q000187:drug effects / Q000201:enzymology*; D010634:Phenobarbital / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D013045:Species Specificity; D013053:Spectrophotometry; D013379:Substrate Specificity; D014357:Trypsin
D007527:Isoenzymes; D003577:Cytochrome P-450 Enzyme System; D014357:Trypsin; D010634:Phenobarbital