The glucose catabolism of the genus Brucella: II. Cell-free studies with B. abortus (S-19)

Cell-free extracts of B. abortus (S-19) were assayed for the enzymes of the major pathways of glucose catabolism. Cell-free preparations readily oxidized d-glucose, glucose 6-phosphate, glucose 1-phosphate, fructose 6-phosphate, 6-phosphogluconate, ribose 5-phosphate, and d-glyceraldehyde 3-phosphate. Fructose 1,6-diphosphate was oxidized very slowly. No activity was observed with either pyruvate or acetate. The enzymes of the EMP pathway were demonstrated except for phosphofructokinase. Only weak fructose diphosphate aldolase activity was detected. The glyceraldehyde phosphate dehydrogenase was specific for NAD and was stimulated by arsenate. Glucose 6-phosphate and 6-phosphogluconic acid dehydrogenase activities were demonstrated. Either NADP or NAD could serve as the cofactor for glucose 6-phosphate dehydrogenase while the 6-phosphogluconic acid dehydrogenase appeared to be specific for NAD. Transaldolase, transketolase, ribose phosphate isomerase, and ribulose phosphate 3-epimerase were detected during the anaerobic dissimilation of ribose 5-phosphate. Phosphogluconate dehydratase was not detected; however, phospho-2-keto-3-deoxy-gluconate aldolase was present. The cell-free studies support the data obtained with whole cells that show the bulk of the glucose catabolism in the brucellae is via the HMP pathway operating in conjunction with the TCA cycle.