The glucose-6-phosphatase (G6Pase) system, located at the endoplasmic reticulum (ER) membrane, has been identified as a significant enzymatic system in the regulation of glucose homeostasis and in glycogenolysis (12, 13), and deficiencies responsible for type I glycogen storage disease (14). This evidence concerns the gene G6PC1 and Glycogen storage disease due to glycogenin deficiency.