NAD(P)H dehydrogenase (quinone)

NAD(P)H dehydrogenase (quinone), also known as quinone reductase, is a flavoprotein enzyme that catalyzes the two-electron reduction of quinones to hydroquinones using NADH or NADPH as electron donors. This reaction is vital in cellular redox cycling and detoxification.

The enzyme plays a crucial role in protecting cells from oxidative stress. Quinones are reactive compounds that can participate in redox cycling, generating reactive oxygen species (ROS) such as superoxide radicals, which can damage DNA, proteins, and lipids. By reducing quinones to hydroquinones, NAD(P)H dehydrogenase (quinone) prevents or minimizes the formation of these harmful ROS. The resulting hydroquinones are typically less reactive and more readily conjugated for excretion.

Different isoforms of NAD(P)H dehydrogenase (quinone) exist, exhibiting variations in substrate specificity and cellular localization. One prominent example is NAD(P)H quinone dehydrogenase 1 (NQO1), a cytosolic enzyme that is highly expressed in many tissues and plays a significant role in detoxification and antioxidant defense. Another isoform, NAD(P)H quinone dehydrogenase 2 (NQO2), also exists, though its precise physiological role is still under investigation.

The activity of NAD(P)H dehydrogenase (quinone) can be affected by various factors, including genetic polymorphisms, exposure to certain chemicals (some of which are inducers of enzyme expression), and disease states. Variations in enzyme activity can influence an individual's susceptibility to oxidative stress and certain diseases. Consequently, NAD(P)H dehydrogenase (quinone) is a subject of ongoing research in the context of cancer prevention, neurodegenerative diseases, and other conditions associated with oxidative damage. The enzyme is also involved in the activation of some anti-cancer prodrugs.