醌氧化还原酶1催化三甲基锁醌丙酸还原机制的理论研究OA

Hypoxia-activated prodrugs(HAPs)represent an important therapeutic strategy targeting the hypoxic tumor microenvironment.Trimethyl lock quinone propionic acid(Q3 PA),a quinone-based HAP,can be reduced by quinone oxidoreductase 1(NQO1)under tumor hypoxia,triggering intramolecular cyclization and the release of active pharmacophores.It has been widely employed in the design of antitumor prodrugs and fluorescent probes.However,the specific enzymatic reduction mechanism of Q3PA remains unclear,limiting its further rational optimization.Density functional theory(DFT)and molecular docking methods were employed to systematically investigate the two-electron reduction mechanism of Q3PA mediated by the coenzyme reduced flavin adenine dinucleotide(FADH2)and its interaction mode within the NQO1 active center.By constructing four possible reaction pathways and calculating the structures and energies of each stationary point,the dominant reaction pathway was elucidated:Initially,FADH2 delivered 2e-/1H+to the carbonyl oxygen atom of Q3PA,generating a semiquinone anion intermediate.Subsequently,a histidine residue provided a second proton to form the hydroquinone structure.Finally,intramolecular cyclization yielded a lactone,releasing the pharmacophore.Molecular docking results revealed that the benzoquinone moiety of Q3 PA stacks parallelly above the isoalloxazine ring of FADH2,forming stable π-π interactions.Its carbonyl groups form hydrogen bonds with Tyr126 and Tyr128,while hydrophobic interactions with residues including Pro68,Trp105,Phe106,His161,and Phe178 further ensure precise substrate positioning within the active center.This study elucidated the reduction pathway and key structural features of Q3PA catalyzed by NQO1 at the atomic level,identifies the dominant pathway and rate-determining step,and clarifies the substrate-enzyme recognition mechanism,providing a theoretical basis for the design of novel hypoxia-targeted antitumor drugs.