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) pa thway and has a very low phosphofructokinase activity. In contrast, this ba cterium exhibits all the enzymes of the pentose phosphate pathway, which ap pears to be the main route for hexose catabolism. 6-Phosphogluconate dehydr ogenase from this bacterium and from B. japonicum USDA 110 has been purifie d 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 th at commits hexoses to the pentose phosphate pathway. (C) 2001 Elsevier Scie nce Ltd. All rights reserved.