10qv
Crystal Structure of NQO1 Complexed with S-Warfarin
Structural highlights
FunctionNQO1_HUMAN The enzyme apparently serves as a quinone reductase in connection with conjugation reactions of hydroquinons involved in detoxification pathways as well as in biosynthetic processes such as the vitamin K-dependent gamma-carboxylation of glutamate residues in prothrombin synthesis. Publication Abstract from PubMedThe NAD(P)H:quinone oxidoreductase (NQO1) has also been described as DT-diaphorase and vitamin K reductase. This enzyme serves to reduce quinones including menadiones (vitamin K derivatives). This activity is thought to suppress the reactivity of the soluble quinone pool by accumulation of less reactive hydroquinols. Though it has been alluded to, the role of NQO1 in vitamin K recycling during thrombosis has not been definitively accounted for. Using transient-state kinetics methods, equilibrium titration and X-ray structural methods, we have examined both the observable catalytic steps of human NQO1 reacting with ubiquinone and the interaction of the enzyme with the anticoagulant, warfarin. These data show that the rate of turnover was governed primarily by the rate of release of ubiquinol. The reductive half-reaction data indicated a limiting rate of reduction of the active site flavin of approximately 1300 s(-1), while reoxidation of the flavin by the reduction of ubiquinone was too rapid to be observed by rapid mixing methods and so must occur at >2000 s(-1). The rate of ubiquinol release however was measured by competition with the process of reduction by NADH and was found to be approximately 370 s(-1); a value consistent with the measured turnover number of approximately 350 s(-1). The reduction potential of the active site FAD cofactor was measured as quite positive at -138 mV and the stereochemistry of the hydride transfer of the reductive half reaction was confirmed from kinetic isotope effects using NAD(2)H isomers as ProR. It was also shown that both the S and R isomers of warfarin bind tightly to NQO1 suppressing activity by competing with the binding of native substrates. The structure of the NQO1*S-warfarin complex was solved to 1.8â¯A resolution and revealed a binding mode similar to that previously observed for dicoumarol. Structural and kinetic analysis of human NQO1: Evidence for therapeutic inhibition by racemic warfarin.,Alt TB, Corrigan MC, Krawczykowski KJ, Smith CO, Vargas AL, Liu D, Moran GR Arch Biochem Biophys. 2026 Sep;783:110911. doi: 10.1016/j.abb.2026.110911. Epub , 2026 Jun 26. PMID:42362135[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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