NADPH dehydrogenase (quinone)

NADPH dehydrogenase (quinone), also frequently referred to as NADPH quinone reductase (NQR), is a flavoprotein enzyme that catalyzes the two-electron reduction of quinones to quinols using NADPH as an electron donor. This reaction is an important step in various metabolic pathways, including antioxidant defense, detoxification, and the biosynthesis of certain molecules.

NQR enzymes are widely distributed across different organisms, including bacteria, plants, and animals. Different forms of the enzyme exist, sometimes membrane-bound and sometimes soluble, with varying specificities for different quinones.

The primary function of NADPH dehydrogenase (quinone) is to detoxify quinones, which can be generated by oxidative stress or exposure to certain xenobiotics. Quinones can undergo redox cycling, generating reactive oxygen species (ROS) that can damage cellular components. By reducing quinones to quinols, NQR enzymes prevent this redox cycling and protect cells from oxidative damage. The resulting quinols are generally less reactive and can be conjugated for excretion.

In addition to detoxification, NADPH dehydrogenase (quinone) plays a role in the biosynthesis of certain essential molecules. For example, in some bacteria, NQR is involved in the biosynthesis of vitamin K.

The activity of NADPH dehydrogenase (quinone) can be influenced by various factors, including the availability of NADPH, the concentration of quinones, and the presence of inhibitors or activators. Some pharmaceutical drugs and environmental pollutants can act as inhibitors of NQR, potentially disrupting cellular redox balance. Conversely, other compounds can act as activators, enhancing the enzyme's activity and providing increased protection against oxidative stress.