Glucose-6-phosphatase 3 (G6PC3) associated with the endoplasmic reticulum membrane catalyzes the hydrolysis of glucose-6-phosphate to glucose and orthophosphate. This reaction is essentially irreversible (Guionie et al. 2003; Ghosh et al. 2004). In the body, this enzyme is ubiquitously expressed; mutations that inactivate it are associated with severe congenital neutropenia (but not with fasting hypoglycemia or lactic acidemia) (Boztug et al. 2009).