More potent inhibition of human CYP2A6 than mouse CYP2A5 enzyme activities by derivatives of phenylethylamine and benzaldehyde.
1. A rapid 96-well plate assay method was developed and validated to measure liver microsomal coumarin 7-hydroxylation in vitro. 2. The method was used to test inhibition of human and mouse CYP2A enzymes by three phenylethylamine derivatives 2-(p-tolyl)-ethylamine, amphetamine, 2-phenylethylamine and benzaldehyde, and two of its derivatives, 4-methylbenzaldehyde and 4-methoxybenzaldehyde. 3. The benzaldehyde derivatives were more potent inhibitors of CYP2A5 than the phenylethylamines. The K(ic) value of 4-methylbenzaldehyde was 3.4 micro M and for 4-methoxybenzaldehyde it was 0.86 micro M for CYP2A5. 4. Amphetamine is a weak inhibitor of CYP2A6, whereas benzaldehyde is a suicide inhibitor with K(inact) = 0.16 min(-1) and K(I) = 18 micro M. The K(ic) values of 2-phenylethylamine, 2-(p-tolyl)-ethylamine, 4-methylbenzaldehyde and 4-methoxybenzaldehyde were 1.13, 0.23, 0.36 and 0.73 micro M for CYP2A6, respectively. 5. Novel potent inhibitors were found for CYP2A6 and, except for 4-methoxybenzaldehyde, all the compounds inhibited CYP2A5 and CYP2A6 enzymes differentially. These data add to the refinement of CYP2A enzyme active sites and provide chemical leads for developing novel chemical inhibitors of the CYP2A6 enzyme.
Department of Pharmacology and Toxicology, University of Kuopio, POB 1627, 70211 Kuopio, Finland.
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D000818:Animals; D001189:Aryl Hydrocarbon Hydroxylases / Q000037:antagonists & inhibitors*; D001547:Benzaldehydes / Q000737:chemistry / Q000494:pharmacology*; D001667:Binding, Competitive; D065637:Cytochrome P-450 CYP2A6; D000072467:Cytochrome P450 Family 2; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D006801:Humans; D020128:Inhibitory Concentration 50; D007700:Kinetics; D051379:Mice; D008862:Microsomes, Liver / Q000201:enzymology; D006899:Mixed Function Oxygenases / Q000037:antagonists & inhibitors*; D010627:Phenethylamines / Q000737:chemistry / Q000494:pharmacology*; D012044:Regression Analysis; D013329:Structure-Activity Relationship
D001547:Benzaldehydes; D004791:Enzyme Inhibitors; D010627:Phenethylamines; D006899:Mixed Function Oxygenases; D001189:Aryl Hydrocarbon Hydroxylases; C585710:CYP2A6 protein, human; C585520:Cyp2a5 protein, mouse; D065637:Cytochrome P-450 CYP2A6; D000072467:Cytochrome P450 Family 2