L-lactate dehydrogenase(lldD) is present in a various organisms, including plants and animals. lldD is an oxidoreductase which catalyses the interconversion of pyruvate and lactate with concurrent interconversion of NADH and NAD+. Seeing that lldD can catalyze the oxidation of hydroxybutyrate, it is occasionally called Hydroxybutyrate Dehydrogenase(HBD).