NAD(P)+transhydrogenase (NNT) is located in the inner mitochondrial membrane and catalyzes a reversible hydride transfer between NAD(H) and NADP(H) that is coupled to proton translocation between the intermembrane space and mitochondrial matrix. NNT activity has an essential role in maintaining the NADPH supply for antioxidant defense and biosynthetic pathways. Structurally, NNT is composed of three domains, domains I and III are hydrophilic and have binding sites for NAD and NADP, respectively, while domain II is hydrophobic and is a transmembrane pathway through which protons translocate. NNT forms dimers, whose monomers act in an anti-phase way, domain III (NADP(H)- binding) flips, allowing proton translocation across the inner mitochondrial membrane one moment and favoring hydride transfer between NAD(H) and NADP(H) the next. And NNT pathophysiological roles after the discovery of a spontaneous Nnt mutation in C57BL/6J mice. And Nnt silencing reduced the growth of cancer cell lines, suggesting that NNT might be a therapeutic target in some cancers.
