The principal products of pentose phosphate pathway are ribose 5-phosphate and NADPH. The transaldolase and transketolase reactions convert excess ribose 5-phosphate to glycolytic intermediates when the metabolic needs for NADPH excess that of ribose 5-phosphate in nucleotide biosynthesis. The resulting gap and fructose 6-phosphate can be consumed through glycolysis and oxidative phosphorylation by gluconeogenesis.

Flux through the pentose phosphate pathway, and thus the rate of NADPH production is controlled by the rate of glucose 6-phosphate dehydrogenase reaction. The activity of this enzyme, which catalyses the pathway’s first committed step, is regulated by NADP⁺ concentration (regulation by substrate availability). When the cell consumes NADPH, the NADP⁺ concentration rises, increasing the rate of glucose 6-phosphate dehydrogenase reaction and, therefore, stimulating NADPH regeneration. In some tissues, the amount of enzyme synthesised also appears to be under hormonal control. Deficient of glucose 6-phosphate dehydrogenase results in syndrome of hemolytic anemia, and Wernicke-Korsakoff syndrome is associated with transketolase activity (genetic disorder).