Serine hydroxymethyltransferase, mitochondrial (UniProt: P34897; also known as EC: 2.1.2.1, SHMT, Glycine hydroxymethyltransferase, Serine methylase) is encoded by the SHMT2 gene (Gene ID: 6472) in human. SHMT is involved in the de novo mitochondrial thymidylate biosynthesis pathway via its role in glycine and tetrahydrofolate metabolism. Thymidylate biosynthesis is required to prevent uracil accumulation in mtDNA. SHMT catalyzes the reversible conversion of serine and glycine. It uses pyridoxal-5 -phosphate as a cofactor. SHMT is synthesized with a transit peptide (aa 1-29) that is needed for its mitochondrial translocation. In eukaryotes two forms of SHMT have been reported: cytosolic and mitochondrial. In the presence of bound pyridoxal 5'-phosphate it is present in a homotetrameric form and in the absence of pyridoxal 5'-phosphate it exists as a homodimer. Pyridoxal 5'-phosphate binding mediates an important conformation change, which is essential for its tetramerization. Three isoforms of SHMT have been reported that are produced by alternative splicing.