THE ENTNER-DOUDOROFF PATHWAY IN HELICOBACTER-PYLORI

Evidence for the presence of the enzymes of the Entner-Doudoroff pathw ay in Helicobacter pylori was obtained using H-1 and P-31 nuclear magn etic resonance spectroscopy. Bacterial lysates generated 6-phosphogluc onate and NADH or NADPH in incubations with glucose-6-phosphate and NA D(+) or NADP(+), indicating the presence of glucose-6-phosphate dehydr ogenase activities. Formation of pyruvate was observed in time courses of incubations of bacterial lysates with 6-phosphogluconate as the on ly substrate, suggesting the presence of 6-phosphogluconate dehydratas e and 2-keto-3-deoxy-6-phosphogluconate aldolase activities. The exist ence of these enzymes and of triose phosphate isomerase was confirmed by observing the appearance of dihydroxyacetone phosphate in time cour ses of bacterial lysates incubated with 6-phosphogluconate. Aldolase a ctivity was measured by the production of pyruvate and dihydroxyaceton e phosphate in lysates incubated with 2-keto-3-deoxy-6-phosphogluconat e as the sole substrate. Dehydrogenase, dehydratase and aldolase activ ities were observed in several bacterial strains including wild types from fresh isolates. Kinetic parameters were measured for the three ac tivities. The cellular location of the enzymes was investigated by com paring the activities measured in the pellet and supernatant fractions obtained by centrifugation of lysate suspensions. The concentration o f compounds causing 50% inhibition of enzyme activity was determined f rom dose-response curves. The data suggested the presence of two gluco se-6-phosphate dehydrogenases linked to NAD(+) and NADP+ activities. U sing inhibitors differences between the H. pylori and mammalian KDPG a ldolases were detected. The presence of these enzyme activities in H. pylori provided evidence for the existence of the Entner-Douderoff pat hway in the bacterium. (C) 1994 Academic Press, Inc.