Hexose-6-Phosphate Dehydrogenase (H6PD)

GDH (EC 1.1.1.47) is a microsomal enzyme that uses NAD or NADP as coenzyme to oxidize glucose-6-phosphate and glucose, as well as other hexose-6-phosphates. It is present in liver, kidney, and leukocytes, but absent from red cells and serum. That it is a dimeric protein is indicated by the presence of 3 bands in mouse-man somatic cell hybrids.

G6PD occurs in 2 forms, H and G. Only the G form, which is X-linked, is found in red cells. Both forms are found in most other tissues. The H form shows activity with other hexose-6-phosphates, especially galactose-6-phosphate, whereas the G form is specific for glucose-6-phosphate.H6PD gene spans 37 kb and consists of 5 exons, the fifth of which codes for more than half of the 89-kD protein.