Interconverts simultaneously and stereospecifically pyruvate and lactate with concomitant interconversion of NADH and NAD(+). (S)-lactate + NAD(+) = H(+) + NADH + pyruvate Fermentation; pyruvate fermentation to lactate; (S)-lactate from pyruvate: step 1/1. Homotetramer (PubMed:11276087). Interacts with PTEN upstream reading frame protein MP31; the interaction leads to inhibition of mitochondrial lactate dehydrogenase activity, preventing conversion of lactate to pyruvate in mitochondria (PubMed:33406399). Predominantly expressed in aerobic tissues such as cardiac muscle. The disease is caused by variants affecting the gene represented in this entry. Belongs to the LDH/MDH superfamily. LDH family. Lactate dehydrogenase entry Another dark horse - Issue 109 of September 2009