Vitamin K (menaquinone) biosynthesis in bacteria: purification and probable structure of an intermediate prior to...

The first aromatic intermediate in the menaquinone biosynthetic pathway is o-succinylbenzoate (OSB); it is formed from chorismate/isochorismate and 2-ketoglutarate. Cell-free extracts of menD+ E. coli strains synthesize an intermediate, "X", which is converted to OSB by extracts of menC+ cells. "X" has been purified to near homogeneity by HPLC. On treatment with acid, it yields both OSB and succinylbenzene (SB). This and other data, suggest that "X" has the structure, 2-succinyl-6-hydroxy-2,4-cyclohexadiene-1-carboxylate (I).