Chemical evolution of the citric acid cycle: sunlight photolysis of the amino acids glutamate and aspartate.

Sunlight photolysis of the amino acids glutamate and aspartate were carried out on 0.1 M aqueous solutions at pH = 7.0. The non-volatile products were identified by GC-MS analysis of derived methyl esters. The major product from glutamic acid was succinic acid, and, analogously, aspartic acid photolyzed to malonic acid. The photochemical oxidative decarboxylation of glutamate parallels its metabolism in modern cells and may provide an evolutionary link between simple amino acids and reactions of the citric acid cycle.