1,3-bisphosphoglycerate (1,3BPG) is the first energy rich intermediate of glycolysis. Cytosolic glucose 1,6-bisphosphate synthase (PGM2L1) utilises 1,3BPG as a phosphate donor to phosphorylate a series of 1-phosphate sugars. Although 5- and 6-phosphate sugars are poor substrates for PGM2L1, glucose 6-phosphate (G6P) is the exception (Maliekal et al. 2007, Veiga-da-Cunha et al. 2008). PGM2L1 complexed with Mg2+ as cofactor, phosphorylates G6P to glucose 1,6-bisphosphate (G1,6BP), a cofactor for phosphomutases and a putative regulator of glycolysis. PGM2L1 is mainly expressed in brain where its activity is particularly high (Maliekal et al. 2007).