InterPro: IPR008141 Alanine dehydrogenase/pyridine nucleotide transhydrogenase

Alanine dehydrogenases (EC:1.4.1.1) and pyridine nucleotide transhydrogenase (EC:1.6.1.1) have been shown to share regions of similarity [1]. Alanine dehydrogenase catalyzes the NAD-dependent reversible reductive amination of pyruvate into alanine. Pyridine nucleotide transhydrogenase catalyzes the reduction of NADP⁺ to NADPH with the concomitant oxidation of NADH to NAD⁺. This enzyme is located in the plasma membrane of prokaryotes and in the inner membrane of the mitochondria of eukaryotes. The transhydrogenation between NADH and NADP is coupled with the translocation of a proton across the membrane. In prokaryotes the enzyme is composed of two different subunits, an alpha chain (gene pntA) and a beta chain (gene pntB), while in eukaryotes it is a single chain protein. The sequence of alanine dehydrogenase from several bacterial species are related with those of the alpha subunit of bacterial pyridine nucleotide transhydrogenase and of the N-terminal half of the eukaryotic enzyme. The two most conserved regions correspond respectively to the N-terminal extremity of these proteins and to a central glycine-rich region which is part of the NAD(H)-binding site.