Glucose-6-phosphate dehydrogenase is the committed step of the hexose monophosphate shunt pathway (pentose phosphate pathway). The enzymes of this pathway are present in the cytoplasm of all cells, but are especially prevalent in adipose and liver cells. The hexose monophosphate shunt pathway makes ribose-5-phosphate for nucleotide synthesis, interconves 6 carbon sugars and 5 carbon sugars, and produces NADPH. NADPH, the reduced form of nicotinamide adenine dinucleotide phosphate, is used in reductive biosynthetic reactions such as fatty acid synthesis, and in the regeneration of glutathione by glutathione reductase. Glutathione has three main roles in a cell: it keeps the protein sulfhydryl groups of cysteines reduced, it reduces peroxides, and it maintains hemoglobin in the reduced state. NADP+ is also involved in this reaction, but as a substrate, rather than a product. The various forms of NAD and FAD do not take pa. Ref: Bender D.A., Mayes P.A. (2011). Chapter 21. The Pentose Phosphate Pathway & Other Pathways of Hexose Metabolism. In D.A. Bender, K.M. Botham, P.A. Weil, P.J. Kennelly, R.K. Murray, V.W. Rodwell (Eds), Harper's Illustrated Biochemistry, 29e.