Pentose phosphate pathway as the main route for hexose catabolism in Bradyrhizobium sp. lacking Entner–Doudoroff pathway. A role for NAD+-dependent 6-phosphogluconate dehydrogenase (decarboxylating)

Bradyrhizobium sp. (Chamaecytisus) BGA-1 lacks the Entner–Doudoroff (ED) pathway and has a very low phosphofructokinase activity. In contrast, this bacterium exhibits all the enzymes of the pentose phosphate pathway, which appears to be the main route for hexose catabolism. 6-Phosphogluconate dehydrogenase from this bacterium and from B. japonicum USDA 110 has been purified to homogeneity. Both enzymes were specific for NAD and they catalyzed the decarboxylation of 6-phosphogluconate to give a ketopentose phosphate as a product. We propose that 6-phosphogluconate dehydrogenase is the enzyme that commits hexoses to the pentose phosphate pathway.