The oxidative phase of the pentose phosphate pathway consists of three reactions (Figure 8.14a). In the first reaction, glucose-6-phosphate dehydrogenase (G-6-PD) catalyzes the oxidation of glucose-6-phosphate. 6-Phosphogluconolactone and NADPH are products in this reaction. 6-Phospho-D-glucono--lactone is then hydrolyzed to produce 6-phospho-D-gluconate. A second molecule of NADPH is produced during the oxidative decarboxylation of 6-phosphogluconate, a reaction that yields ribulose-5-phosphate.