Abstract
Dog CYP2A13 and CYP2A25 were coexpressed with dog NADPH-cytochrome P450 reductase (OR) in baculovirus-infected Sf9 insect cells. CYP2A13 effectively catalyzed 7-ethoxycoumarin (7EC) deethylation and coumarin hydroxylation with apparent Km values of 4.8 and 2.1 μM, respectively, similar to those observed using dog liver microsomes (7.5 and 0.75 μM, respectively). CYP2A25 exhibited much lower affinity toward 7EC, with an apparent Km value of 150 μM, which indicates that CYP2A13 plays a more significant role in the metabolism of these CYP2A substrates. Similar to the dog CYP1A2 enzyme, CYP2A13 efficiently catalyzed phenacetin deethylation with a Km value of 3.9 μM, which suggests that phenacetin is not a selective probe for dog CYP1A2 activity. Both dog CYP2A13 and CYP2A25 exhibited little or no catalytic activity toward other common cytochrome P450 probe substrates, including bupropion, amodiaquine, diclofenac, S-mephenytoin, bufuralol, dextromethorphan, midazolam, and testosterone. These results provided additional information about the selectivity of these commonly used probe substrates.
Footnotes
Article, publication date, and citation information can be found at http://dmd.aspetjournals.org.
doi:10.1124/dmd.110.033068.
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ABBREVIATIONS:
- P450
- cytochrome P450
- OR
- NADPH-cytochrome P450 reductase
- PCR
- polymerase chain reaction
- 7EC
- 7-ethoxycoumarin.
- Received March 2, 2010.
- Accepted April 9, 2010.
- Copyright © 2010 by The American Society for Pharmacology and Experimental Therapeutics
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