Inhibitory potency of 8-methoxypsoralen on cytochrome P450 2A6 (CYP2A6) allelic variants CYP2A6 15, CYP2A6 16, CYP2A6 21 and CYP2A6 22: differential susceptibility due to different sequence locations of the mutations.
Human cytochrome P450 2A6 (CYP2A6) is a highly polymorphic isoform of CYP2A subfamily. Our previous kinetic study on four CYP2A6 allelic variants (CYP2A6 15, CYP2A6 16, CYP2A6 21 and CYP2A6 22) have unveiled the functional significance of sequence mutations in these variants on coumarin 7-hydroxylation activity. In the present study, we further explored the ability of a typical CYP2A6 inhibitor, 8-methoxypsoralen (8-MOP), in inhibition of these alleles and we hypothesized that translational mutations in these variants are likely to give impact on 8-MOP inhibitory potency. The CYP2A6 variant and the wild type proteins were subjected to 8-MOP inhibition to yield IC50 values. In general, a similar trend of change in the IC50 and Km values was noted among the four mutants towards coumarin oxidation. With the exception of CYP2A6 16, differences in IC50 values were highly significant which implied compromised interaction of the mutants with 8-MOP. Molecular models of CYP2A6 were subsequently constructed and ligand-docking experiments were performed to rationalize experimental data. Our docking study has shown that mutations have induced enlargement of the active site volume in all mutants with the exception of CYP2A6 16. Furthermore, loss of hydrogen bond between 8-MOP and active site residue Asn297 was evidenced in all mutants. Our data indicate that the structural changes elicited by the sequence mutations could affect 8-MOP binding to yield differential enzymatic activities in the mutant CYP2A6 proteins.
School of Pharmacy and Health Sciences, International Medical University, Kuala Lumpur, Malaysia.
Kai Hung
KH
Tiong
Jeffrey Cheah School of Medicine and Health Sciences, Monash University Malaysia, Bandar Sunway, Selangor, Malaysia.
Nafees Ahemad
NA
Mohammed Yunus
School of Pharmacy and Health Sciences, International Medical University, Kuala Lumpur, Malaysia.
Beow Chin
BC
Yiap
School of Pharmacy and Health Sciences, International Medical University, Kuala Lumpur, Malaysia.
Eng Lai
EL
Tan
Centre of Excellence for Research in AIDS (CERiA), Universiti Malaya, Kuala Lumpur, Malaysia.
Rusli
R
Ismail
Discipline of Pharmacy, Monash University Malaysia, Bandar Sunway, Selangor, Malaysia.
Chin Eng
CE
Ong
D001189:Aryl Hydrocarbon Hydroxylases / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000235:genetics*; D065637:Cytochrome P-450 CYP2A6; D004926:Escherichia coli; D014644:Genetic Variation; D006801:Humans; D020128:Inhibitory Concentration 50; D007527:Isoenzymes / Q000235:genetics; D008730:Methoxsalen / Q000494:pharmacology*; D008958:Models, Molecular; D015394:Molecular Structure; D009154:Mutation / Q000235:genetics; D011485:Protein Binding; D011487:Protein Conformation; D013329:Structure-Activity Relationship
D007527:Isoenzymes; D001189:Aryl Hydrocarbon Hydroxylases; C585710:CYP2A6 protein, human; D065637:Cytochrome P-450 CYP2A6; D008730:Methoxsalen