Molecular docking and oxidation kinetics of 3-phenyl coumarin derivatives by human CYP2A13

Abstract

1.CYP2A13 enzyme is expressed in human extrahepatic tissues, while CYP2A6 is a hepatic enzyme. Reactions catalyzed by CYP2A13activate tobacco-specificnitrosamines and some other toxic xenobioticsin lungs. 2.To compare oxidation characteristics and substrate-enzyme active site interactions in CYP2A13 vs CYP2A6, we evaluatedCYP2A13 mediated oxidationcharacteristics of 23coumarin derivatives and modelled their interactionsatthe enzyme active site.3.CYP2A13 did not oxidizesix coumarin derivatives to corresponding fluorescent 7-hydroxycoumarins. The Km-values of the other coumarinsvaried 0.85–97 μM,Vmax-values of the oxidation reaction varied 0.25–60 min-1, and intrinsic clearance varied 26–6190 kL/min*mol CYP2A13). Kmof 6-chloro-3-(3-hydroxyphenyl)-coumarin was 0.85(0.55-1.15 95 % confidence limit)μM and Vmax0.25(0.23-0.26)min-1, whereas Kmof6-hydroxy-3-(3-hydroxyphenyl)-coumarin was 10.9 (9.9-11.8) μM and Vmax60 (58–63) min-1. Docking analysesdemonstrated that 6-chloro or 6-methoxy and 3-(3-hydroxyphenyl) or 3-(4-trifluoromethylphenyl) substituents of coumarin increasedaffinity to CYP2A13, whereas 3-triazole or 3-(3-acetate phenyl) or 3-(4-acetatephenyl) substituents decreasedit.4.The active site of CYP2A13 accepts more diversified types of coumarin substrates than the hepatic CYP2A6 enzyme.New sensitive and convenient profluorescent CYP2A13 substrates were identified, such as 6-chloro-3-(3-hydroxyphenyl)-coumarin having high affinity and 6-hydroxy-3-(3-hydroxyphenyl)-coumarin with high intrinsic clearance.