Succinyl CoA and glycine condense to form 5-aminolevulinate (ALA) Authored: Jassal, B, D'Eustachio, P, 2007-01-24 10:19:49 EC Number: 2.3.1.37 Edited: Jassal, B, D'Eustachio, P, 2007-01-24 10:19:49 Pubmed16121195 Pubmed1939222 Reactome Database ID Release 43189442 Reactome, http://www.reactome.org ReactomeREACT_9463 Reviewed: Sassa, S, 2007-01-24 10:18:36 The committed step for porphyrin synthesis is the formation of 5-aminolevulinate (ALA) by condensation of glycine (from the general amino acid pool) and succinyl-CoA (from the TCA cycle), in the mitochondrial matrix. The reaction is catalyzed by two different ALA synthases, one expressed ubiquitously (ALAS1) and the other only expressed in erythroid precursors (ALAS2). Both enzymes are expressed as homodimers and require pyridoxal 5-phosphate as a cofactor.<br>No disease-causing mutations of ALAS1 have been recognised in humans. Mutations in ALAS2 cause X-linked sideroblastic anaemia (XLSA), characterised by a microcytic hypochromic anaemia.