Biosynthesis of o-succinylbenzoic acid in a men- Escherichia coli mutant requires decarboxylation of L-glutamate at the C-1 position.

A men- mutant of Escherichia coli, AN 209, which accumulates o-succinylbenzoic acid, has been used for a direct study of the biosynthesis of this benzenoid compound. Samples of labeled glutamic acids were added to growth media, and the o-succinylbenzoic acid was isolated and converted to a dimethyl derivative. This dimethyl derivative was purified on thin-layer chromatograms and by gas chromatography. When the glutamic acid used as precursor contained 14C at position 5, or was uniformly labeled, the dimethyl o-succinylbenzoate contained radioactivity (as shown by radiogas chromatography). However, from [1-14C]glutamate, the dimethyl o-succinylbenzoate was without radioactivity. Hence, in the biosynthesis of o-succinylbenzoate, carbon atom 1 of glutamate is lost, and carbon atoms 2-5 are retained. It was also shown that this mutant lacked the enzyme dihydroxynaphthoic acid synthase. It should, therefore, continue to be classified as a menB mutant, rather than as a member of the newly created menE group (lacking o-succinylbenzoate-CoA synthetase).