o-Succinylbenzoate—CoA ligase (EC 6.2.1.26), encoded from the menE gene in Escherichia coli, catalyzes the fifth reaction in the synthesis of menaquinone (vitamin K2). This pathway is called 1, 4-dihydroxy-2-naphthoate biosynthesis I.[1] Vitamin K is a quinone that serves as an electron transporter during anaerobic respiration. This process of anaerobic respiration allows the bacteria to generate the energy required to survive.
| o-Succinylbenzoate—CoA ligase | |||||||||
|---|---|---|---|---|---|---|---|---|---|
 A cartoon representation of O-succinylbenzoate Co-A ligase of Staphylococcus aureus (strain N315). The different subunits are shown in different colors. | |||||||||
| Identifiers | |||||||||
| EC no. | 6.2.1.26 | ||||||||
| CAS no. | 72506-70-8 | ||||||||
| Databases | |||||||||
| IntEnz | IntEnz view | ||||||||
| BRENDA | BRENDA entry | ||||||||
| ExPASy | NiceZyme view | ||||||||
| KEGG | KEGG entry | ||||||||
| MetaCyc | metabolic pathway | ||||||||
| PRIAM | profile | ||||||||
| PDB structures | RCSB PDB PDBe PDBsum | ||||||||
| |||||||||
Background
The systematic name for the MenE enzyme is 2-succinylbenzoate: CoA ligase (AMP-forming). Other names for this enzyme include: o-succinylbenzoate-CoA synthase; o-succinylbenzoyl-coenzyme A synthetase; OSB-CoA synthetase; OSB: CoA ligase; synthetase, and o-succinylbenzoyle coenzyme A. The EC number is 6.2.1.26. MenE belongs to the ligase enzyme family, or class 6.
In the presence of 0.5mM of Ca(2+), K(+), Na(+), and Zn(2+) the enzyme activity was increased twofold. In the presence of .5 mM of Co(2+) and Mn(2+) the enzyme activity was increased fourfold. Mg(2+) is the ion that increases the enzyme activity the most. With .5 mM of Mg(2+) enzyme activity was increased sixfold. Inhibitors of this enzyme include diethylprocarbonate, Fe(2+), Hg(2+), and Mg(2+) (above 1mM).[2]
The maximum specific enzymatic activity is 3.2 micromol/min/mg. The optimum pH is 7.5. The maximum pH is 8. The optimum temperature is 30 degrees Celsius and the maximum temperature is 40 degrees Celsius. The molecular weight of o-succinylbenzoate CoA ligase is 185000 Da or 185 kDa. This enzyme is a tetramer, meaning it has four subunits in its quaternary structure.[2]
The PDB accession code is 3ipl. This is the crystal structure for o-succinylbenzoate CoA ligase in Staphylococcus aureus (strain N315) because the structure for E. coli has not been crystallized as of yet.[3]
Pathway
The pathway o-succinylbenzoate CoA ligase belongs to is called 1, 4-dihydroxy-2-napthoate biosynthesis I. Other organisms that contain this pathway are eukaryotic bacteria such as Bacillus anthracis.[4] Organisms that contain a pathway similar to this include Arabidopsis thaliana (gene AAE14),[5] Mycobacterium phlei,[6] and Synechocystis sp. (gene PCC 6803).[7] The reason for the difference in pathways is due to the varying functions of Vitamin K. Eukaryotic bacteria use vitamin K II while other organisms use vitamin K I. Other pathways that include o-succinylbenzoate CoA ligase include 1, 4-diydroxy-2-naphthoate biosynthesis II (i.e. in Arabidopsis thaliana), biosynthesis of secondary metabolites, metabolic pathways, ubiquinone, and other terpenoid-quinone biosynthesis. In Bacillus anthracis this enzyme is a target of potential antibiotic discovery.
Reaction
The reaction in vitamin K synthesis that includes MenE is as follows:
ATP + 2-succinylbenzoate + CoA = AMP + diphosphate + 4-(2-carboxyphenyl)-4-oxobutanoyl-CoA
The substrates of this reaction are ATP, CoA, and 2-succinylbenzoate. The cofactors are ATP and CoA. The products are AMP, diphosphate, and 4-(2-carboxyphenyl)-4-oxobutanoyl-CoA.[8]
References
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