Interconverts simultaneously and stereospecifically pyruvate and lactate with concomitant interconversion of NADH and NAD(+). (S)-lactate + NAD(+) = H(+) + NADH + pyruvate Fermentation of pyruvate to lactate is inhibited when bound to folliculin FLCN, perhaps partly by FLCN preventing binding of cofactor NADH (PubMed:34381247). Fermentation; pyruvate fermentation to lactate; (S)-lactate from pyruvate: step 1/1. Homotetramer (PubMed:11276087). Interacts with PTEN upstream reading frame protein MP31 (PubMed:33406399). Interacts with folliculin FLCN; the interaction is direct and inhibits enzymatic activity (PubMed:34381247). Predominantly expressed in anaerobic tissues such as skeletal muscle and liver. ISGylated. 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