title: Inhibition of CYP2B4 by 2-ethynylnaphthalene: evidence for the co-binding of substrate and inhibitor within the active site.
abstract: 2-ethynylnaphthalene (2EN) is an effective mechanism-based inhibitor of CYP2B4. There are two inhibitory components: (1) irreversible inactivation of CYP2B4 (a typical time-dependent inactivation), and (2) a reversible component. The reversible component was unusual in that the degree of inhibition was not simply a characteristic of the enzyme-inhibitor interaction, but dependent on the size of the substrate molecule used to monitor residual activity. The effect of 2EN on the metabolism of seven CYP2B4 substrates showed that it was not an effective reversible inhibitor of substrates containing a single aromatic ring; substrates with two fused rings were competitively inhibited by 2EN; and larger substrates were non-competitively inhibited. Energy-based docking studies demonstrated that, with increasing substrate size, the energy of 2EN and substrate co-binding in the active site became unfavorable precisely at the point where 2EN became a competitive inhibitor. Hierarchical docking revealed potential allosteric inhibition sites separate from the substrate binding site.
authors.affiliation: Department of Pharmacology and Experimental Therapeutics, The Stanley S. Scott Cancer Center, Louisiana State University Health Sciences Center, 533 Bolivar Street, New Orleans, LA 70112, USA.
authors.forename: Dongmei
authors.initials: D
authors.lastname: Cheng
authors.forename: Danni
authors.initials: D
authors.lastname: Harris
authors.forename: James R
authors.initials: JR
authors.lastname: Reed
authors.forename: Wayne L
authors.initials: WL
authors.lastname: Backes
mesh_terms: D001189:Aryl Hydrocarbon Hydroxylases / Q000037:antagonists & inhibitors* / Q000648:ultrastructure*; D001665:Binding Sites; D003198:Computer Simulation; D000072467:Cytochrome P450 Family 2; D004789:Enzyme Activation; D008956:Models, Chemical; D008958:Models, Molecular; D009281:Naphthalenes / Q000737:chemistry*; D011485:Protein Binding; D013379:Substrate Specificity
chemical_list: D009281:Naphthalenes; C065012:2-ethynylnaphthalene; D001189:Aryl Hydrocarbon Hydroxylases; D000072467:Cytochrome P450 Family 2; C465241:cytochrome P-450 CYP2B4 (rabbit)