InterPro: IPR002811 Aspartate dehydrogenase

This group contains aspartate dehydrogenases that belong to a unique class of amino acid dehydrogenases.

The structure of Thermotoga maritima TM1643 has been found to contain an N-terminal Rossmann fold domain (which binds the NAD(⁺) cofactor) and a C-terminal alpha/beta domain [1]. This suggested that TM1643 may be a dehydrogenase with the active site located at the interface between the two domains. Enzymatic characterisation of TM1643 revealed that it possesses NAD or NADP-dependent dehydrogenase activity toward l-aspartate but no aspartate oxidase activity [1]. The product of the aspartate dehydrogenase activity is also iminoaspartate. It has been suggested that two different enzymes, an oxidase and a dehydrogenase, may have evolved to catalyse the first step of NAD biosynthesis [1]. Members of this group share some structural similarity to several other NAD(P)⁺-dependent oxidoreductases, including inositol 1-phosphate synthase, dihydrodipicolinate reductase, and ASA-DH [1].

It has been proposed that in Thermotoga maritima, TM1643 catalyses the first reaction of de novo biosynthesis of NAD from aspartate, and it produces iminoaspartate required for this pathway. The formation of an enzyme complex between TM1643 and NadA, the next enzyme of the pathway, may allow the channeling of this unstable product directly to the NadA active site [1].

The same domain is present in animals (e.g., Caenorhabditis elegans F17C8.3 protein).