This definition appears rarely
1. 27) and D-lactate dehydrogenases (D-LDH: D-lactate:NAD+ oxidoreductase, EC 1. 1. 1. 28) as well as by NAD-independent (cytochrome) enzymes (DLD: D-lactate ferricytochrome c oxidoreductase, EC 1. 1. 2. 4). Despite their apparent functional similarity, these classes of enzymes are selective for the D/L chirality of the substrate . Studies on the primary amino acid structures of L-LDH and D-LDH suggest that the genes encoding them are not evolutionarily related [2,3] and that their products belong to larger families of enzymes: L(-)-LDHs belong to the L-specific NAD-dependent dehydrogenases, while D(+)-LDHs belong to the D-isomer specific 2-hydroxy acid dehydrogenases and the FAD-binding oxidoreductase/transferase type 4 family.