The G6PC gene encodes glucose-6-phosphatase, an integral membrane enzyme of the endoplasmic reticulum. The enzyme is responsible for the breakdown of glucose-6-phosphate into glucose, and hence plays a key role in maintaining glucose homeostasis through the pathways of gluconeogenesis and glycogenolysis. The enzyme is also involved in cholesterol homeostasis and regulation of gene expression.
In the absence of the G6PC enzyme, glucose-6-phosphatase is instead converted to fat and glycogen which accumulates in the cells. This toxic accumulation causes tissue and organ damage and eventually results in Glycogen Storage Disease Ia (GSD1a), a disorder characterized by growth retardation, hepatomegaly, lactic acidosis and hypoglycemia.