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The pentose phosphate pathway is a metabolic mechanism that runs in the opposite direction of glycolysis.In the pentose phosphate pathway, NADPH and pentoses are produced, as well as ribose 5-phosphate, a nucleotide synthesis precursor. While the pentose phosphate route does involve glucose oxidation, it serves primarily as an anabolic process.

G6PD (glucose-6-phosphate dehydrogenase) is an enzyme that regulates the levels of NADPH in cells as part of the pentose phosphate pathway. G6PD is selective for ${\mathrm{NADP}}^{+}$and inhibited by NADPH.

The G6PD enzyme catalyzes the following reaction:

$\mathrm{glucose}-6-\mathrm{phosphate}+{\mathrm{NADP}}^{+}+{\mathrm{H}}_2\mathrm{O}⇌6-\mathrm{phosphoglucono}-\mathrm{δ\pm ô²¹³¦³Ù´Ç²Ô\pm ð}+\mathrm{NADPH}+{\mathrm{H}}^{+}$

Neutrophils and macrophages produce superoxide. In reactive oxygen species processes, glucose-6-phosphate dehydrogenase (G6PDH) is involved. The NADPH concentration in the cell is maintained through the pentose phosphate pathway. The pentose phosphate pathway is aided by G6PDH and ${\mathrm{NAD}}^{+}$. The conversion of molecular oxygen to reactive oxygen species requires electrons. The cell is harmed by reactive oxygen species (ROS). The activity of NADPH oxidase raises the level of ${\mathrm{NAD}}^{+}$. To reduce the number of cases of ${\mathrm{NAD}}^{+}$in the cell, $\mathrm{G}6\mathrm{PDH}$increases to use ${\mathrm{NAD}}^{+}$to produce NADPH. As a result, the formation of reactive oxygen species is avoided.