o-Succinylbenzoate synthase (OSBS) catalyzes the conversion of 2-succinyl-6-hydroxy-2,4-cyclohexadiene-1-carboxylate (SHCHC) to 4-(2'-carboxyphenyl)-4-oxobutyrate (o-succinylbenzoate or OSB), a reaction in the menaquinone biosynthetic pathway. Menaquinone is an essential cofactor for anaerobic growth in eubacteria and some archaea. OSBS belongs to the enolase superfamily of enzymes, characterized by the presence of an enolate anion intermediate which is generated by abstraction of the alpha-proton of the carboxylate substrate by an active site residue and is stabilized by coordination to the essential Mg2+ ion.
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