Phosphogluconic Dehydrogenase in Higher Plants

Abstract

A phosphogluconic dehydrogenase dependent on TPN has been demonstrated in wheat germ, cantaloupe and cucumber fruits, parsley and spinach leaves, and parsnip and turnip roots. Since all plant sources tested contained glutathione reductase, the oxidation of phosphogluconate was coupled with the reduction of GSSG, and pentose orcinol-reacting material and CO2 were shown to be formed as products of such reactions. The stoichiometry indicated the occurrence of other reactions in addition to the oxidation of phosphogluconate to pentose and CO2. A prepn. from parsley leaves caused a disappearance of ribose-5-phosphate, with an appearance of the qualitative test for 7-carbon ketoses and an unidentified TPN dependent oxidative step.