title: Substrate proton to heme distances in CYP2C9 allelic variants and alterations by the heterotropic activator, dapsone.
abstract: CYP2C9 polymorphisms result in reduced enzyme catalytic activity and greater activation by effector molecules as compared to wild-type protein, with the mechanism(s) for these changes in activity not fully elucidated. Through T(1) NMR and spectral binding analyses, mechanism(s) for these differences in behavior of the variant proteins (CYP2C9.2, CYP2C9.3, and CYP2C9.5) as compared to CYP2C9.1 were assessed. Neither altered binding affinity nor substrate (flurbiprofen) proton to heme-iron distances differed substantially among the four enzymes. Co-incubation with dapsone resulted in reduced substrate proton to heme-iron distances for all enzymes, providing at least a partial mechanism for the activation of CYP2C9 variants by dapsone. In summary, neither altered binding affinity nor substrate orientation appear to be major factors in the reduced catalytic activity noted in the CYP2C9 variants, but dapsone co-incubation caused similar changes in substrate proton to heme-iron distances suggesting at least partial common mechanisms in the activation of the CYP2C9 forms.
authors.affiliation: Department of Experimental and Clinical Pharmacology, College of Pharmacy, University of Minnesota, 7-115B Weaver-Densford Hall, 308 Harvard Street, SE, Minneapolis, MN 55455, USA.
authors.forename: Matthew A
authors.initials: MA
authors.lastname: Hummel
authors.forename: Peter M
authors.initials: PM
authors.lastname: Gannett
authors.forename: Jarrett
authors.initials: J
authors.lastname: Aguilar
authors.forename: Timothy S
authors.initials: TS
authors.lastname: Tracy
mesh_terms: D000483:Alleles; D000890:Anti-Infective Agents / Q000494:pharmacology*; D001189:Aryl Hydrocarbon Hydroxylases / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D001665:Binding Sites; D065729:Cytochrome P-450 CYP2C9; D003622:Dapsone / Q000737:chemistry / Q000494:pharmacology*; D006418:Heme / Q000737:chemistry*; D007700:Kinetics; D015394:Molecular Structure; D009154:Mutation; D019906:Nuclear Magnetic Resonance, Biomolecular; D011485:Protein Binding; D011522:Protons; D013379:Substrate Specificity
chemical_list: D000890:Anti-Infective Agents; D011522:Protons; D006418:Heme; D003622:Dapsone; C450260:CYP2C9 protein, human; D065729:Cytochrome P-450 CYP2C9; D001189:Aryl Hydrocarbon Hydroxylases