PGM1 is an evolutionarily conserved enzyme that regulates one of the most important metabolic carbohydrate trafficking points in prokaryotic and eukaryotic organisms, catalyzing the bi-directional interconversion of glucose 1-phosphate (G-1-P) and glucose 6-phosphate (G-6-P). In one direction, G-1-P produced from sucrose catabolism is converted to G-6-P, the first intermediate in glycolysis. In the other direction, conversion of G-6-P to G-1-P generates a substrate for synthesis of UDP-glucose, which is required for synthesis of a variety of cellular constituents, including cell wall polymers and glycoproteins. PGM1 has been used extensively as a genetic marker for isozyme polymorphism among humans. PGM is known to be post-translationally modified by cytoplasmic glycosylation that does not seem to regulate its enzymatic activity but rather is implicated in the localization of the protein. Glucose 1,6 bisphosphate (Glc-1, 6-P2), a powerful regulator of carbohydrate metabolism, has been demonstrated to be a potent activator of PGM. PGM1 is also modified by phosphorylation on Ser108 as part of its catalytic mechanism. This is shown to be performed by Pak1, a previously identified signaling kinase.