NOX (EC 1.6.99.3) is widely present in animals, plants, microorganisms, and cultured cells. It can directly oxidize NADH to NAD in the presence of oxygen. This enzyme not only participates in NAD regeneration but is also closely associated with immune responses.
Assay Principle: NOX catalyzes the oxidation of NADH to NAD. This oxidation is coupled with the reduction of 2,6-dichlorophenolindophenol (DCPIP). The blue DCPIP is reduced to its colorless form. The activity of NADH oxidase is determined by measuring the rate of reduction of blue DCPIP at 600 nm.