Azoreductase/NQO1 Protein, Human

Azoreductase/NQO1 protein is a flavin-containing quinone reductase that facilitates the two-electron reduction of quinones to hydroquinones, utilizing either NADH or NADPH as electron donors. Operating through a ping-pong kinetic mechanism, the electrons are sequentially transferred from NAD(P)H to the flavin cofactor and subsequently to the quinone, effectively bypassing the generation of semiquinone and reactive oxygen species. This enzymatic activity plays a crucial role in regulating cellular redox balance by detoxifying quinones. Azoreductase/NQO1 serves as a superoxide scavenger, preventing hydroquinone oxidation and supporting antioxidant defense mechanisms. Moreover, it participates in the activation of quinones, generating redox-reactive hydroquinones with potential antitumor properties through DNA cross-linking. Notably, the protein acts as a gatekeeper for the core 20S proteasome, interacting with tumor suppressors TP53 and TP73 in a NADH-dependent manner to inhibit their ubiquitin-independent degradation during oxidative stress.