The Entner-Doudoroff pathway in Helicobacter pylori.

Evidence for the presence of the enzymes of the Entner-Doudoroff pathway in Helicobacter pylori was obtained using 1H and 31P nuclear magnetic resonance spectroscopy. Bacterial lysates generated 6-phosphogluconate and NADH or NADPH in incubations with glucose-6-phosphate and NAD+ or NADP+, indicating the presence of glucose-6-phosphate dehydrogenase activities. Formation of pyruvate was observed in time courses of incubations of bacterial lysates with 6-phosphogluconate as the only substrate, suggesting the presence of 6-phosphogluconate dehydratase and 2-keto-3-deoxy-6-phosphogluconate aldolase activities. The existence of these enzymes and of triose phosphate isomerase was confirmed by observing the appearance of dihydroxyacetone phosphate in time courses of bacterial lysates incubated with 6-phosphogluconate. Aldolase activity was measured by the production of pyruvate and dihydroxyacetone phosphate in lysates incubated with 2-keto-3-deoxy-6-phosphogluconate as the sole substrate. Dehydrogenase, dehydratase and aldolase activities were observed in several bacterial strains including wild types from fresh isolates. Kinetic parameters were measured for the three activities. The cellular location of the enzymes was investigated by comparing the activities measured in the pellet and supernatant fractions obtained by centrifugation of lysate suspensions. The concentration of compounds causing 50% inhibition of enzyme activity was determined from dose-response curves. The data suggested the presence of two glucose-6-phosphate dehydrogenases linked to NAD+ and NADP+ activities. Using inhibitors differences between the H. pylori and mammalian KDPG aldolases were detected. The presence of these enzyme activities in H. pylori provided evidence for the existence of the Entner-Douderoff pathway in the bacterium.