BIOCHEMICAL CHANGES DURING THE DEVELOPMENT OF RESPIRATORY ACTIVITY IN ESCHERICHIA COLI

II. CHANGES IN ENZYME ACTIVITIES

Abstract

Cell-free extracts were prepared from four types of Escherichia coli cells; cells grown aerobically with glucose, cells grown aerobically without glucose, cells grown anaerobically with glucose, and cells obtained after aeration of the anaerobically grown cells. Examination of the activities of about 20 enzymes in these extracts showed that glucose and oxygen in growth environment generally do not significantly influence the level of enzymes in fermentative pathways. The presence of oxygen during the growth increased the level of formate dehydrogenase, NADH oxidase system, and several enzymes in the tricarboxylic acid cycle, particularly isocitrate dehydrogenase and succinyl-CoA synthetase. The presence of glucose during the growth repressed the level of several enzymes in the glyoxylate cycle, particularly isocitrate lyase and citrate synthase. When thick suspensions of the cells grown anaerobically with glucose were aerated in a glucose-free incubation mixture for 4hr, initial low activities of about 10 enzymes increased to the level of cells grown aerobically in the absence of glucose, without accompanying significant cell multiplication.