G6PC1 and hyperinsulinemic hypoglycemia, familial, 4: When applied to the neutropenia in GSD1b and G6PC3 deficiency, this concept led to the discovery that the molecule that intoxicates neutrophils was 1,5-anhydroglucitol-6-phosphate (1,5-AG6P), a compound without any known function that is structurally similar to glucose-6-phosphate and a known inhibitor of hexokinase 1, which is normally kept at a very low concentration by the combined activity of two proteins endowed with metabolite repair activity: G6PT and G6PC3 [17] (Figure 2).