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CYP2C9‐CYP3A4 protein‐protein interactions in a reconstituted expressed enzyme system
Author(s) -
Subramanian Murali,
Zhang Helen,
Tracy Timothy S
Publication year - 2008
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.22.1_supplement.919.7
Subject(s) - cyp3a4 , chemistry , cyp2c9 , metabolite , cytochrome p450 , enzyme , biochemistry , microsome , in vivo , metabolism , demethylation , enzyme assay , isozyme , biology , gene expression , gene , microbiology and biotechnology , dna methylation
Protein‐protein interactions between cytochrome P450 isoforms can alter catalytic activity and may confound in‐vitro in‐vivo correlations. The interaction between CYP2C9 and CYP3A4, two highly abundant P450s in human liver and responsible for 70% of the P450 oxidation reactions carried out, were studied for their ability to affect catalysis. Reconstituted, expressed human CYP2C9, CYP3A4 and P450 reductase (CPR) were co‐incubated with lipids, substrate and NADPH, and rate of metabolite formation measured. CYP3A4 inhibited the CYP2C9‐mediated S‐flurbiprofen (4’‐hydroxylation) and S‐naproxen (O‐demethylation) metabolism up to 70%, depending on enzyme ratios and amount of CPR present; these effects were only partially reversed by additional CPR. High concentrations (50 μM) of dapsone (a CYP2C9 activator) decreased CYP3A4 inhibition by 20%, whereas lower concentrations of dapsone had no effect. When evaluated in the converse, the presence of CYP3A4 appeared to enhance dapsone activation due to a lower baseline CYP2C9 activity. It is hypothesized that an active site conformational change occurs when CYP2C9 and CYP3A4 interact. In conclusion, it appears that the presence of the abundant P450 enzyme CYP3A4 may alter CYP2C9 activity and thus, potentially confound in vitro – in vivo predictions of drug metabolism and disposition. Support: NIH GM063215.