Quinone reductase 2 (NQO2) (NQO2)

Quinone reductase 2 (NQO2), historically characterized as the MT3 melatonin binding site, is a cytosolic flavoenzyme that functions as an oxidoreductase (UniProt P16083). Unlike the MT1 and MT2 receptors, which are G protein-coupled receptors, MT3/NQO2 catalyzes the two-electron reduction of quinones and their derivatives using N-ribosyldihydronicotinamide (NRH) as a co-substrate (PubMed: 10713453). It is expressed in various tissues, including the brain, liver, and heart, where it contributes to the regulation of the cellular redox state and the detoxification of xenobiotics (PubMed: 21114957). Melatonin binds to the catalytic site of NQO2 with high affinity, acting as a potent inhibitor of the enzyme's activity, which may explain some of melatonin's non-receptor-mediated antioxidant effects (IUPHAR/BPS Guide to Pharmacology). Dysregulation of NQO2 has been linked to neurodegenerative diseases such as Alzheimer's and Parkinson's, as well as certain types of cancer, making it a target of interest for pharmacological intervention (PubMed: 25660174). Drugs such as the alpha-blocker prazosin and the polyphenol resveratrol are known to interact with this site, providing tools for studying its physiological roles (PubMed: 15173111).

Other names

MT3Melatonin receptor type 3NAD(P)H:quinone oxidoreductase 2QR2Ribosyldihydronicotinamide dehydrogenase [quinone]

Competitive inhibition of the enzymatic reduction of quinones and modulation of cellular redox state.