6-phosphogluconolactonase

6-Phosphogluconolactonase (EC 3.1.1.31, 6PGL, PGLS, systematic name 6-phospho-D-glucono-1,5-lactone lactonohydrolase) 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-gluconate

The tertiary structure of 6PGL employs an α/β hydrolase fold, with active site residues clustered on the loops of the α-helices. Based on the crystal structure of the enzyme, the mechanism is proposed to be dependent on proton transfer by a histidine residue in the active site. 6PGL selectively catalyzes the hydrolysis of δ-6-phosphogluconolactone, and has no activity on the γ isomer.