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The Molecular and Enzyme Kinetic Basis for Altered Activity of Three Cytochrome P450 2C19 Variants Found in the Chinese Population

[ Vol. 13 , Issue. 3 ]

Author(s):

Amelia Nathania Dong, Nafees Ahemad, Yan Pan, Uma Devi Palanisamy, Beow Chin Yiap and Chin Eng Ong*   Pages 233 - 244 ( 12 )

Abstract:


Background: There is a large inter-individual variation in cytochrome P450 2C19 (CYP2C19) activity. The variability can be caused by the genetic polymorphism of CYP2C19 gene. This study aimed to investigate the molecular and kinetics basis for activity changes in three alleles including CYP2C19*23, CYP2C19*24 and CYP2C19*25found in the Chinese population.

Methods: The three variants expressed by bacteria were investigated using substrate (omeprazole and 3- cyano-7-ethoxycoumarin[CEC]) and inhibitor (ketoconazole, fluoxetine, sertraline and loratadine) probes in enzyme assays along with molecular docking.

Results: All alleles exhibited very low enzyme activity and affinity towards omeprazole and CEC (6.1% or less in intrinsic clearance). The inhibition studies with the four inhibitors, however, suggested that mutations in different variants have a tendency to cause enhanced binding (reduced IC50 values). The enhanced binding could partially be explained by the lower polar solvent accessible surface area of the inhibitors relative to the substrates. Molecular docking indicated that G91R, R335Q and F448L, the unique mutations in the alleles, have caused slight alteration in the substrate access channel morphology and a more compact active site cavity hence affecting ligand access and binding. It is likely that these structural alterations in CYP2C19 proteins have caused ligand-specific alteration in catalytic and inhibitory specificities as observed in the in vitro assays.

Conclusion: This study indicates that CYP2C19 variant selectivity for ligands was not solely governed by mutation-induced modifications in the active site architecture, but the intrinsic properties of the probe compounds also played a vital role.

Keywords:

Cytochrome P450 2C19, genetic polymorphism, Chinese, site-directed mutagenesis, enzyme assays, molecular docking.

Affiliation:

School of Pharmacy, Monash University Malaysia, Jalan Lagoon Selatan, 47500 Bandar Sunway, Selangor, School of Pharmacy, Monash University Malaysia, Jalan Lagoon Selatan, 47500 Bandar Sunway, Selangor, Department of Biomedical Science, University of Nottingham Malaysia Campus, Jalan Broga, 43500 Semenyih, Selangor, Jeffrey Cheah School of Medicine and Health Sciences, Monash University Malaysia, Jalan Lagoon Selatan, 47500 Bandar Sunway, Selangor, School of Pharmacy, International Medical University, 126, Jalan Jalil Perkasa 19, Bukit Jalil, 57000 Kuala Lumpur, School of Pharmacy, International Medical University, 126, Jalan Jalil Perkasa 19, Bukit Jalil, 57000 Kuala Lumpur

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