H6PD

There are 2 forms of glucose-6-phosphate dehydrogenase. G form is X-linked and H form, encoded by this gene, is autosomally linked. This H form shows activity with other hexose-6-phosphates, especially galactose-6-phosphate, whereas the G form is specific for glucose-6-phosphate. Both forms are present in most tissues, but H form is not found in red cells.

Full Name

hexose-6-phosphate dehydrogenase (glucose 1-dehydrogenase)

Function

Bifunctional enzyme localized in the lumen of the endoplasmic reticulum that catalyzes the first two steps of the oxidative branch of the pentose phosphate pathway/shunt, an alternative to glycolysis and a major source of reducing power and metabolic intermediates for biosynthetic processes (By similarity).

Has a hexose-6-phosphate dehydrogenase activity, with broad substrate specificity compared to glucose-6-phosphate 1-dehydrogenase/G6PD, and catalyzes the first step of the pentose phosphate pathway (PubMed:12858176, PubMed:18628520, PubMed:23132696).

In addition, acts as a 6-phosphogluconolactonase and catalyzes the second step of the pentose phosphate pathway (By similarity).

May have a dehydrogenase activity for alternative substrates including glucosamine 6-phosphate and glucose 6-sulfate (By similarity).

The main function of this enzyme is to provide reducing equivalents such as NADPH to maintain the adequate levels of reductive cofactors in the oxidizing environment of the endoplasmic reticulum (PubMed:12858176, PubMed:18628520, PubMed:23132696).

By producing NADPH that is needed by reductases of the lumen of the endoplasmic reticulum like corticosteroid 11-beta-dehydrogenase isozyme 1/HSD11B1, indirectly regulates their activity (PubMed:18628520).

Biological Process

Glucose metabolic process Source: UniProtKB-KW
Pentose-phosphate shunt, oxidative branch Source: UniProtKB
Regulation of cortisol biosynthetic process Source: UniProtKB
Response to alcohol Source: Ensembl

Cellular Location

Endoplasmic reticulum lumen

Involvement in disease

Cortisone reductase deficiency 1 (CORTRD1):
An autosomal recessive error of cortisone metabolism characterized by a failure to regenerate cortisol from cortisone, resulting in increased cortisol clearance, activation of the hypothalamic-pituitary axis and ACTH-mediated adrenal androgen excess. Clinical features include hyperandrogenism resulting in hirsutism, oligo-amenorrhea, and infertility in females and premature pseudopuberty in males.