Cofactors

Mn(2+) or Mg(2+).

Reaction Mechanism

o-succinylbenzoate synthase By Reference

o-Succinylbenzoate synthase (OSBS) is a member of the muconate lactonising enzyme subgroup of the enolase superfamily. It catalyses the exergonic dehydration reaction in the menaquinone biosynthesis pathway in which 2-succinyl-6-hydroxy-2,4-cyclohexadiene-1-carboxylate (SHCHC) is converted to o-succinylbenzoate.




• Summary
• Step 1
• Step 2
• Products

The dehydration is initiated by the abstraction of a proton from the C1, the carbon adjacent to the carboxylate group by Lys133, forming an enediolate anion intermediate. The negatively charged intermediate is stabilised by Lys235 through a cation-pi interaction to the cyclohexadienyl moiety and by Mg(II) ion through a bidentate coordination to the carboxylate group. Lys133 is also responsible for protonation of the departing water molecule.

Catalytic Residues

AA	Uniprot	Uniprot Resid	PDB	PDB Resid
Lys	P29208	133	1r6w	135
Asp	P29208	161	1r6w	163
Glu	P29208	190	1r6w	192
Asp	P29208	213	1r6w	215
Lys	P29208	235	1r6w	237

Step Components

overall product formed, native state of enzyme regenerated, overall reactant used, dehydration, proton transfer, aromatic unimolecular elimination by the conjugate base



Step 1.

Lys133 abstracts a proton from the substrate.



Step 2.

The intermediate eliminates water with concomitant deprotonation of Lys133 to form the final product and regenerate the enzyme's active site.



Products.

The products of the reaction.

View Reaction Mechanisms in M-CSA

Reaction Parameters

• Kinetic Parameters

  Organism	KM Value [mM]	Substrate	Comment
  Thermobifida fusca	0.61	(1R,6R)-6-hydroxy-2-succinylcyclohexa-2,4-diene-1-carboxylate	pH 8.0, 25°C, recombinant mutant N73L/T75V
  Escherichia coli	3.8	(1R,6R)-6-hydroxy-2-succinylcyclohexa-2,4-diene-1-carboxylate	pH 8.0, 25°C, recombinant mutant G288A
  Exiguobacterium sp.	2600	(1R,6R)-6-hydroxy-2-succinylcyclohexa-2,4-diene-1-carboxylate	pH 8.0, 25°C, recombinant enzyme

• Temperature

  Organism	Temperature Range	Comment
  Escherichia coli	37 - 60	about 30% of maximal activity at 37°C and at 60°C

• pH

  Organism	pH Range	Comment
  Escherichia coli	7.5 - 9	pH 7.5: about 60% of maximal activity, pH 9.0: about 60% of maximal activity

Associated Proteins

Citations

• Comparison of Alicyclobacillus acidocaldarius o-Succinylbenzoate Synthase to Its Promiscuous N-Succinylamino Acid Racemase/ o-Succinylbenzoate Synthase Relatives.
• Second-Shell Amino Acid R266 Helps Determine N-Succinylamino Acid Racemase Reaction Specificity in Promiscuous N-Succinylamino Acid Racemase/o-Succinylbenzoate Synthase Enzymes.
• Divergent evolution of ligand binding in the o-succinylbenzoate synthase family.
• Enzyme promiscuity in enolase superfamily. Theoretical study of o-succinylbenzoate synthase using QM/MM methods.
• Promiscuity of Exiguobacterium sp. AT1b o-succinylbenzoate synthase illustrates evolutionary transitions in the OSBS family.
• Molecular modeling and docking studies of O-succinylbenzoate synthase of M. tuberculosis--a potential target for antituberculosis drug design.
• Residues required for activity in Escherichia coli o-succinylbenzoate synthase (OSBS) are not conserved in all OSBS enzymes.
• Roles of the second-shell amino acid R266 in other members of the MLE subgroup of the enolase superfamily
• Rewiring the respiratory pathway of Lactococcus lactis to enhance extracellular electron transfer.
• Natural Composition and Biosynthetic Pathways of Alkaloids in Medicinal Dendrobium Species.
• Comparative transcriptome analysis of different tissues of Rheum tanguticum Maxim. ex Balf. (Polygonaceae) reveals putative genes involved in anthraquinone biosynthesis.