SAICAR => AICAR + Fumarate 5'-phosphoribosyl-5-aminoimidazole-4-N-succinocarboxamide (SAICAR) <=> 5'-phosphoribosyl-5-aminoimidazole-4-carboxamide (AICAR) + fumarate Authored: D'Eustachio, P, 2004-02-12 14:16:00 EC Number: 4.3.2.2 Edited: D'Eustachio, P, Jassal, B, 0000-00-00 00:00:00 Pubmed10958654 Pubmed18388293 Pubmed8366112 Reactome Database ID Release 4373800 Reactome, http://www.reactome.org ReactomeREACT_1463 The reversible conversion of 5'-phosphoribosyl-5-aminoimidazole-4-N-succinocarboxamide (SAICAR) to 5'-phosphoribosyl-5-aminoimidazole-4-carboxamide (AICAR) and fumarate is catalyzed by adenylosuccinate lyase. The active form of this enzyme is a cytosolic tetramer (Stone et al. 1993), and fluoresence microscopy of cultured human cells suggests that it may associate with other enzymes of de novo IMP biosynthesis under some metabolic conditions (An et al. 2008). The enzyme also catalyzes the conversion of adenylosuccinate to adenosine 5'-monophosphate and fumarate. Humans lacking the enzyme accumulate dephosphorylated forms of both substrates, indicating that the enzyme mediates both reactions in vivo as well (Race et al. 2000).