Glucose-6-phosphate isomerase, or phosphoglucose isomerase, is an enzyme that catalyzes the reversible interconversion of glucose-6-phosphate into fructose-6-phosphate in the second step of of the Embden-Meyerhof glycolytic pathway. There is evidence that phosphoglucose isomerase acts as a molecular messenger. It is produced and secreted by white blood cells, and acts to regulate the growth of several different cell types. A deficiency of phosphoglucose isomerase is responsible for the hemolytic anemias.
The functional form of the Glucose-6-phosphate isomerase is a dimer. Each molecule is divided into two globular domains and a C-terminal tail. Both domains have a central core of a beta pleated sheet flanked by α-helices to form a typical alpha/beta folding motif. The active site is situated in a cleft between the large and small domains of the monomer and is formed by the association of the two subunits. There are several Glucose-6-phosphate isomerases from different organisms reported by the CSGID: from Vibrio cholerae (idp01329), Bacillus anthracis (idp01650) and Staphylococcus aureus (idp00736).