Accepted name: acireductone synthase
Reaction: 5-(methylsulfanyl)-2,3-dioxopentyl phosphate + H2O = 1,2-dihydroxy-5-(methylsulfanyl)pent-1-en-3-one + phosphate (overall reaction)
(1a) 5-(methylsulfanyl)-2,3-dioxopentyl phosphate = 2-hydroxy-5-(methylsulfanyl)-3-oxopent-1-enyl phosphate (probably spontaneous)
(1b) 2-hydroxy-5-(methylsulfanyl)-3-oxopent-1-enyl phosphate + H2O = 1,2-dihydroxy-5-(methylsulfanyl)pent-1-en-3-one + phosphate
Glossary: acireductone = 1,2-dihydroxy-5-(methylsulfanyl)pent-1-en-3-one
Other name(s): E1; E-1 enolase-phosphatase; 5-(methylthio)-2,3-dioxopentyl-phosphate phosphohydrolase (isomerizing)
Systematic name: 5-(methylsulfanyl)-2,3-dioxopentyl-phosphate phosphohydrolase (isomerizing)
Comments: This bifunctional enzyme first enolizes the substrate to form the intermediate 2-hydroxy-5-(methylsulfanyl)-3-oxopent-1-enyl phosphate, which is then dephosphorylated to form the acireductone 1,2-dihydroxy-5-(methylsulfanyl)pent-1-en-3-one [2]. The acireductone represents a branch point in the methione-salvage pathway as it is used in the formation of formate, CO and 3-(methylsulfanyl)propanoate by EC [acireductone dioxygenase (Ni2+-requiring)] and of formate and 4-(methylsulfanyl)-2-oxobutanoate either by a spontaneous reaction under aerobic conditions or by EC {acireductone dioxygenase [iron(II)-requiring]} [1,2].
1.  Myers, R.W., Wray, J.W., Fish, S. and Abeles, R.H. Purification and characterization of an enzyme involved in oxidative carbon-carbon bond cleavage reactions in the methionine salvage pathway of Klebsiella pneumoniae. J. Biol. Chem. 268 (1993) 24785–24791. [PMID: 8227039]
2.  Wray, J.W. and Abeles, R.H. The methionine salvage pathway in Klebsiella pneumoniae and rat liver. Identification and characterization of two novel dioxygenases. J. Biol. Chem. 270 (1995) 3147–3153. [PMID: 7852397]
3.  Wang, H., Pang, H., Bartlam, M. and Rao, Z. Crystal structure of human E1 enzyme and its complex with a substrate analog reveals the mechanism of its phosphatase/enolase activity. J. Mol. Biol. 348 (2005) 917–926. [PMID: 15843022]
[EC created 2006]

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