Glucose 6-phosphate isomerase is a well study enzyme that catalyzes one of the first steps in the glycolysis pathway, conversion of glucose 6-phosphate to fructose 6-phosphate. The molecule acts as a homodimer with two active sites formed in the interface between monomers. Although there are two monomers in the asymmetric unit of this crystal form, this is not the biological dimer. The biological dimer can be created for both chains via symmetry operations. Glucose 6-phosphate isomerase from a variety of different organisms has been solved, such as Geobacillus stearothermophilus, Thermus thermophilus, Mus musculus and Homo sapiens. The bacterial examples have the best structural similarity with S. aureus glucose 6-phosphate isomerase, but it is a very well conserved enzyme and also aligns well with the human and mouse versions. The protein has been previously crystallized with a variety of substrate analogues and inhibitors, such as 6-phosphogluconic acid (2CXR), erythose-4-phosphate (1IRI), and n-bromoacetyl-aminoethyl phosphate (1C7Q). 10mM substrate was added to the mother liquor during crystallization. There is very weak electron density overlaying the location where the phosphate and attached carbon of substrate analogues bind, but the rest is disordered. One copy of a linear sugar could be visualized distant from the active site on the surface of the molecule.
Chou, C.-C., Sun, Y.-J., Meng, M., Hsiao, C.. (2000) The crystal structure of phosphoglucose isomerase/autocrine motility factor/neuroleukin complexed with its carbohydrate phosphate inhibitors suggests its substrate/receptor recognition J.Biol.Chem. 275: 23154-23160