Accepted name: 2-succinyl-5-enolpyruvyl-6-hydroxy-3-cyclohexene-1-carboxylic-acid synthase
Reaction: isochorismate + 2-oxoglutarate = 5-enolpyruvoyl-6-hydroxy-2-succinylcyclohex-3-ene-1-carboxylate + CO2
For diagram of reaction, click here.
Other name(s): SEPHCHC synthase; MenD
Systematic name: isochorismate:2-oxoglutarate 4-oxopentanoatetransferase (decarboxylating)
Comments: Requires Mg2+ for maximal activity. This enzyme is involved in the biosynthesis of vitamin K2 (menaquinone). In most anaerobes and all Gram-positive aerobes, menaquinone is the sole electron transporter in the respiratory chain and is essential for their survival. It had previously been thought that the products of the reaction were (1R,6R)-6-hydroxy-2-succinylcyclohexa-2,4-diene-1-carboxylate (SHCHC), pyruvate and CO2 but it is now known that two separate enzymes are involved: this enzyme and EC 18.104.22.168, 2-succinyl-6-hydroxy-2,4-cyclohexadiene-1-carboxylate synthase. Under basic conditions, the product can spontaneously lose pyruvate to form SHCHC.
Links to other databases: BRENDA, EXPASY, KEGG, Metacyc, PDB, CAS registry number: 1112282-73-1
1. Jiang, M., Cao, Y., Guo, Z.F., Chen, M., Chen, X. and Guo, Z. Menaquinone biosynthesis in Escherichia coli: identification of 2-succinyl-5-enolpyruvyl-6-hydroxy-3-cyclohexene-1-carboxylate as a novel intermediate and re-evaluation of MenD activity. Biochemistry 46 (2007) 10979-10989. [PMID: 17760421]