Glucose-6-phosphate dehydrogenase (EC: 1.1.1.49) (G6PDH) is a ubiquitous protein, present in bacteria and all eukaryotic cell types [PMID:2838391]. The enzyme catalyses the the first step in the pentose pathway, i.e. the conversion of glucose-6-phosphate to gluconolactone 6-phosphate in the presence of NADP, producing NADPH. The ubiquitous expression of the enzyme gives it a major role in the production of NADPH for the many NADPH-mediated reductive processes in all cells [PMID:3393536]. Deficiency of G6PDH is a common genetic abnormality affecting millions of people worldwide. Many sequence variants, most caused by single point mutations, are known, exhibiting a wide variety of phenotypes [PMID:3393536].