6-Phosphogluconolactonase is a cytosolic enzyme found in all organisms that catalyzes the hydrolysis of 6-phosphogluconolactone to 6-phosphogluconic acid in the oxidative phase of the pentose phosphate pathway: 6-phospho-D-glucono-1,5-lactone + H2O = 6-phospho-D-gluconateThe tertiary structure of 6PGL employs an α/β hydrolase fold, with active site residues clustered on the loops of the α-helices. Wikipedia