The metabolism of C2-compounds in micro-organisms. 8. A dicarboxylic acid cycle as a route for the oxidation of glycollate by <i>Escherichia coli</i>

Abstract

Although the tricarboxylic acid cycle has been established as the major route for the oxidation of acetate, and of compounds catabolized to acetate, in a wide variety of organisms (for review, see Krebs & Lowenstein, 1960) little is known of the pathways of oxidation of C2 compounds more highly oxidized than acetate, such as glycollate or glyoxylate. The main purpose of this paper is to show that, whereas the tricarboxylic acid cycle plays an essential role in the growth of EWcherichia coli on glycollate as sole carbon source, this cycle is not necessary for glycollate oxidation. The results obtained with the mutant M 22-64 of E. coli, strain w, which is devoid of the citrate-forming condensing enzyme (Gilvarg & Davis, 1957), and with its parent wild type, support the view that glyoxylate, derived from the oxidation of glycollate, can be oxidized completely via a dicarboxylic acid cycle in which glyoxylate condenses with acetylcoenzyme A to form malate, which is oxidized via oxaloacetate and pyruvate to regenerate the acetyl-coenzyme A required for the initial condensa- tion. An outline of this work has been published (Kornberg & Sadler, 1960).