GLYCOLATE METABOLISM IN ESCHERICHIA COLI

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Abstract
This study of glycolate-adapted Escherichia coli indicates that the most probable route for utilization of the substrate includes glyceric acid, 3-phospho-glyceric acid, and the tircarboxylic acid cycle. A glyceric acid dehydrogenase, which reduces tartronic semialdehyde to glycerate in the presence of reduced diphosphopyridine nucleotide, and a kinase, which catalyzes the formation of 3-phosphoglycerate from glyceric acid and adenosine triphosphate, were shown to be present. Carbon recoveries in growing cultures and manometric data obtained with resting cells showed the complete oxidation of glycolate to carbon dioxide. Measurements of the oxidation of tricarboxylic acid cycle intermediates indicated that these compounds are oxidized without lag and at a rate commensurate with the rate of glycolate oxidation. Assays of the enzymes characteristic of known pathways of terminal oxidation, such as isocitratase, malate synthetase, isocitric dehydrogenase, and condensing enzyme, provided further evidence for an operating tricarboxylic acid cycle. A postulated pathway for the utilisation of glycolic acid is as follows glycolate [forward arrow]glycerate [forward arrow] 3-phosphoglycerate [forward arrow] pyruvate [forward arrow] tricarboxylic acid cycle.