Posttranslational modifications of the cytochrome P-450 monooxygenase system

J Cancer Res Clin Oncol. 1987;113(2):155-9. doi: 10.1007/BF00391438.


Two forms of enzymatic posttranslational modifications of the monooxygenase system are described: modification by phosphatase and modification by protein kinase. Phosphatase treatment of microsomes isolated from phenobarbital-pretreated rabbits and rats caused a marked decrease of monooxygenase activity which was paralleled by a comparable decrease of NADPH-cytochrome P-450 reductase activity while the second essential component of the system, cytochrome P-450, remained unaltered. Thus phosphatase attacks monooxygenase via reductase. Protein kinases showed the opposite preference; while cytochrome P-450 was phosphorylated, NADPH-cytochrome P-450 reductase was not. Thus the kinase affects monooxygenase via cytochrome P-450. The phosphorylation of cytochrome P-450 turned out to be a specific reaction observed only with certain cytochrome P-450 isoenzymes and certain protein kinases.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cytochrome P-450 Enzyme System / metabolism*
  • Cytochromes / metabolism
  • Mixed Function Oxygenases / metabolism*
  • NADPH-Ferrihemoprotein Reductase / metabolism
  • Phosphoprotein Phosphatases / metabolism
  • Phosphorylation
  • Protein Kinases / metabolism
  • Protein Processing, Post-Translational
  • Rabbits
  • Rats


  • Cytochromes
  • cytochrome P420
  • Cytochrome P-450 Enzyme System
  • Mixed Function Oxygenases
  • NADPH-Ferrihemoprotein Reductase
  • Protein Kinases
  • Phosphoprotein Phosphatases