Fig. 1

Enzyme deficiencies in glycogen storage disease type 1a vs glycogen storage disease type 1b [15]. In the final step of endogenous glucose production, glucose-6 phosphate enters the endoplasmic reticulum of the cell through a transporter known as G6PT. Upon entering the endoplasmic reticulum the enzyme glucose-6 phosphatase, also known as G6PC, hydrolyzes glucose-6 phosphate into glucose and inorganic phosphate. Glucose then leaves the endoplasmic reticulum and is released systemically. In glycogen storage disease type 1a there is a mutation of the enzyme G6PC resulting in a buildup of glucose-6 phosphate in the endoplasmic reticulum. In glycogen storage disease 1b, there is a mutation of G6PT, whereby glucose-6 phosphate cannot enter the endoplasmic reticulum to undergo the catalytic reaction. G6PT1: glucose 6 phosphate translocase 1, G6PC: glucose 6 phosphatase catalytic subunit, ER: Endoplasmic Reticulum