Involved in the pentose phosphate pathway via hydrolysis of 6-phosphogluconolactone to 6-phosphogluconate. 6-phospho-D-glucono-1,5-lactone + H2O = 6-phospho-D-gluconate + H(+) Carbohydrate degradation; pentose phosphate pathway; D-ribulose 5-phosphate from D-glucose 6-phosphate (oxidative stage): step 2/3. Present with 4320 molecules/cell in log phase SD medium. Belongs to the glucosamine/galactosamine-6-phosphate isomerase family. 6-phosphogluconolactonase subfamily.