Members of this subfamily have an LDH-like structure and an MDH enzymatic activity. Some members, like MJ0490 from Methanococcus jannaschii, exhibit both MDH and LDH activities. Tetrameric MDHs, including those from phototrophic bacteria, are more similar to LDHs than to other MDHs. LDH catalyzes the last step of glycolysis in which pyruvate is converted to L-lactate. MDH is one of the key enzymes in the citric acid cycle, facilitating both the conversion of malate to oxaloacetate and replenishing levels of oxalacetate by reductive carboxylation of pyruvate. The LDH-like MDHs are part of the NAD(P)-binding Rossmann fold superfamily, which includes a wide variety of protein families including the NAD(P)-binding domains of alcohol dehydrogenases, tyrosine-dependent oxidoreductases, glyceraldehyde-3-phosphate dehydrogenases, formate/glycerate dehydrogenases, siroheme synthases, 6-phosphogluconate dehydrogenases, aminoacid dehydrogenases, repressor rex, and NAD-binding potassium channel domains, among others.
Lu S et al.(2020). "CDD/SPARCLE: the conserved domain database in 2020.",