Putative Lactate dehydrogenase and (R)-2-Hydroxyglutarate Dehydrogenase-like proteins, NAD-binding and catalytic domains
This group contains various putative dehydrogenases related to D-lactate dehydrogenase (LDH), (R)-2-hydroxyglutarate dehydrogenase (HGDH), and related enzymes, members of the 2-hydroxyacid dehydrogenases family. LDH catalyzes the interconversion of pyruvate and lactate, and HGDH catalyzes the NAD-dependent reduction of 2-oxoglutarate to (R)-2-hydroxyglutarate. Despite often low sequence identity within this 2-hydroxyacid dehydrogenase family, these proteins typically have a characteristic arrangement of 2 similar subdomains of the alpha/beta Rossmann fold NAD+ binding form. The NAD+ binding domain is inserted within the linear sequence of the mostly N-terminal catalytic domain, which has a similar domain structure to the internal NAD binding domain. Structurally, these domains are connected by extended alpha helices and create a cleft in which NAD is bound, primarily to the C-terminal portion of the 2nd (internal) domain.