Degradation of rat liver cytochromes P450 3A after their inactivation by 3,5-dicarbethoxy-2,6-dimethyl-4-ethyl-1,4-dihydropyridine: characterization of the proteolytic system

Arch Biochem Biophys. 1992 Sep;297(2):228-38. doi: 10.1016/0003-9861(92)90666-k.


The suicide substrate 3,5-dicarbethoxy-2,6-dimethyl-4-ethyl-1,4- dihydropyridine (DDEP) inactivates rat liver cytochrome P450 (P450) 3A isozymes through prosthetic heme alkylation of the apoprotein in a mechanism-based fashion, which marks them for rapid proteolysis. In this article, through the use of epitope-specific monoclonal antibodies, we show that both 3A1 and 3A2 isozymes are targeted for proteolysis. Furthermore, using intact rats, isolated rat hepatocytes, and rat liver subcellular fractions supplemented with ATP and MgCl2, as well as various proteolytic inhibitors as probes, we now report that the hepatic cytosolic ubiquitin-dependent proteolytic system rather than hepatic lysosomes is involved in the rapid degradation of DDEP-induced heme alkylated P450s 3A.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Apoenzymes / metabolism
  • Cells, Cultured
  • Cytochrome P-450 Enzyme Inhibitors
  • Cytochrome P-450 Enzyme System / metabolism*
  • Dexamethasone / pharmacology
  • Dicarbethoxydihydrocollidine / analogs & derivatives*
  • Dicarbethoxydihydrocollidine / pharmacology
  • Isoenzymes / antagonists & inhibitors
  • Isoenzymes / metabolism*
  • Kinetics
  • Liver / drug effects
  • Liver / enzymology*
  • Male
  • Rats
  • Rats, Inbred Strains
  • Subcellular Fractions / enzymology


  • Apoenzymes
  • Cytochrome P-450 Enzyme Inhibitors
  • Isoenzymes
  • 3,5-dicarbethoxy-2,6-dimethyl-4-ethyl-1,4-dihydropyridine
  • Dicarbethoxydihydrocollidine
  • Dexamethasone
  • Cytochrome P-450 Enzyme System