Separation of two constitutive forms of cytochrome P-450 active in aminopyrine N-demethylation from rabbit intestinal mucosa microsomes

Biochim Biophys Acta. 1985 Sep 20;831(1):99-105. doi: 10.1016/0167-4838(85)90155-4.


Two constitutive forms of cytochrome P-450, designated P-450ib and P-450ic, were purified from intestinal mucosa microsomes of untreated rabbits. P-450ib and P-450ic have minimal molecular weights of 56 000 and 49 000, respectively, as determined by calibrated sodium dodecyl sulphate polyacrylamide gel electrophoresis. The CO-reduced difference spectral maximum of cytochrome P-450ib is at 450 nm and P-450ic is at 451 nm. Both the cytochromes preferentially demethylate aminopyrine, benzphetamine and N,N-dimethylaniline in the presence of NADPH-cytochrome P-450 reductase. Cytochrome P-450ib has absorption maxima at 417, 535 and 573 nm in the oxidized form, indicating that this cytochrome is in a low-spin state. Ouchterlony double-diffusion studies show that cytochrome P-450ib does not cross-react with antisera against liver cytochrome P-450LM2 purified from phenobarbital-treated rabbits, but P-450ic cross-reacts with spur formation. Unlike cytochrome P-450ib, P-450ic is very similar, if not identical, to liver cytochrome P-450LM2 on the basis of its molecular weight, spectral properties, catalytic activities and immunochemical properties.

MeSH terms

  • Aminopyrine N-Demethylase / metabolism*
  • Animals
  • Cytochrome P-450 Enzyme System / isolation & purification*
  • Electrophoresis, Polyacrylamide Gel
  • Endopeptidases / metabolism
  • Immunodiffusion
  • Intestinal Mucosa / ultrastructure*
  • Isoenzymes / isolation & purification*
  • Male
  • Microsomes / enzymology*
  • Molecular Weight
  • Papain / metabolism
  • Rabbits
  • Serine Endopeptidases*


  • Isoenzymes
  • Cytochrome P-450 Enzyme System
  • Aminopyrine N-Demethylase
  • Endopeptidases
  • Serine Endopeptidases
  • glutamyl endopeptidase
  • Papain