Nicotinamide Nucleotide Transhydrogenase (NNT)

NNT is a pyridine nucleotide transhydrogenase (EC 1.6.1.1). These integral inner mitochondrial membrane proteins are part of the energy-transfer system of the respiratory chain and catalyze the transfer of a hydride ion between nicotinamide adenine dinucleotide, NAD(H), and oxidized nicotinamide dinucleotide phosphate, NADP(H).

The deduced 1,086-amino acid NNT protein has a 43-amino acid presequence, 10 membrane-spanning alpha helices, and substrate-binding sites for NAD(H) and NADP(H). It shares 97% amino acid identity with bovine Nnt and 94% identity with mouse Nnt. A hypervariable region is located in the first transmembrane helix, and the presequences are less conserved.