Catalyzes the oxidative decarboxylation of 6-phosphogluconate to ribulose 5-phosphate and CO(2), with concomitant reduction of NADP to NADPH. 6-phospho-D-gluconate + NADP(+) = CO2 + D-ribulose 5-phosphate + NADPH Carbohydrate degradation; pentose phosphate pathway; D-ribulose 5-phosphate from D-glucose 6-phosphate (oxidative stage): step 3/3. Homodimer. Present with 101000 molecules/cell in log phase SD medium. Belongs to the 6-phosphogluconate dehydrogenase family.