The crystal structure of phosphoglucose isomerase/autocrine motility factor/neuroleukin complexed with its carbohydrate phosphate inhibitors suggests its substrate/receptor recognition.

Phosphoglucose isomerase catalyzes the reversible isomerization of glucose 6-phosphate to fructose 6-phosphate. In addition, phosphoglucose isomerase has been shown to have functions equivalent to neuroleukin, autocrine motility factor, and maturation factor. Here we present the crystal structures of phosphoglucose isomerase complexed with 5-phospho-D-arabinonate and N-bromoacetylethanolamine phosphate at 2.5- and 2.3-A resolution, respectively. The inhibitors bind to a region within the domains' interface and interact with a histidine residue (His(306)) from the other subunit. We also demonstrated that the inhibitors not only affect the enzymatic activity of phosphoglucose isomerase, but can also inhibit the autocrine motility factor-induced cell motility of CT-26 mouse colon tumor cells. These results indicate that the substrate and the receptor binding sites of phosphoglucose isomerase and autocrine motility factor are located within close proximity to each other. Based on these two complex structures, together with biological and biochemical results, we propose a possible isomerization mechanism for phosphoglucose isomerase.