Multiple roles of glucose-6-phosphatases in pathophysiology: state of the art and future trends.

Background: The endoplasmic reticulum enzyme glucose-6-phosphatase catalyzes the hydrolysis of glucose-6-phosphate to glucose and inorganic phosphate. The enzyme is a part of a multicomponent system that includes several integral membrane proteins; the catalytic subunit (G6PC) and transporters for glucose-6-phosphate, inorganic phosphate and glucose. The G6PC gene family presently includes three members, termed as G6PC, G6PC2, and G6PC3. Although the three isoforms show a moderate amino acid sequence homology, their membrane topology and catalytic site are very similar. The isoforms are expressed differently in various tissues. Mutations in all three genes have been reported to be associated with human diseases.

Scope Of Review: The present review outlines the biochemical features of the G6PC gene family products, the regulation of their expression, their role in the human pathology and the possibilities for pharmacological interventions.

Major Conclusions: G6PCs emerge as integrators of extra- and intracellular glucose homeostasis. Beside the well known key role in blood glucose homeostasis, the members of the G6PC family seem to play a role as sensors of intracellular glucose and of intraluminal glucose/glucose-6-phosphate in the endoplasmic reticulum.

General Significance: Since mutations in the three G6PC genes can be linked to human pathophysiological conditions, the better understanding of their functioning in connection with genetic alterations, altered expression and tissue distribution has an eminent importance.