Comparative analysis of substrate and inhibitor interactions with CYP3A4 and CYP3A5

Xenobiotica. 2006 Apr;36(4):287-99. doi: 10.1080/00498250500446208.


To evaluate the role that cytochrome (CYP) 3A5 plays in hepatic drug metabolism, the substrate selectivity and inhibitory potential of over 60 compounds towards CYP3A4 and CYP3A5 were assessed using Escherichia coli recombinant cell lines. CYP3A4-mediated metabolism predominated for many of the compounds studied. However, a number of drugs gave similar CL(int) estimates using CYP3A5 compared with CYP3A4 including midazolam (CL(int) = 3.4 versus 3.3 microl min(-1) pmol(-1)). Significant CYP3A5-mediated metabolism was also observed for several drugs including mifepristone (CL(int) = 10.3 versus 2.4 microl min(-1) pmol(-1)), and ritonavir (CL(int) = 0.76 versus 0.47 microl min(-1) pmol(-1)). The majority of compounds studied showed a greater inhibitory potential (IC(50)) towards CYP3A4 compared with CYP3A5 (eightfold lower on average). A greater degree of time-dependent inhibition was also observed with CYP3A4 compared with CYP3A5. The range of compounds investigated in the present study extends significantly previous work and suggests that CYP3A5 may have a significant role in drug metabolism particularly in populations expressing high levels of CYP3A5 and/or on co-medications known to inhibit CYP3A4.

Publication types

  • Comparative Study

MeSH terms

  • Cell Line
  • Cytochrome P-450 CYP3A
  • Cytochrome P-450 Enzyme Inhibitors
  • Cytochrome P-450 Enzyme System / chemistry*
  • Drug Interactions
  • Enzyme Inhibitors / pharmacology*
  • Escherichia coli / metabolism
  • Humans
  • Inhibitory Concentration 50
  • Kinetics
  • Microsomes, Liver / enzymology*
  • Mifepristone / pharmacology
  • Ritonavir / pharmacology
  • Substrate Specificity
  • Time Factors


  • Cytochrome P-450 Enzyme Inhibitors
  • Enzyme Inhibitors
  • Mifepristone
  • Cytochrome P-450 Enzyme System
  • CYP3A5 protein, human
  • Cytochrome P-450 CYP3A
  • CYP3A4 protein, human
  • Ritonavir