This is the C-terminal SIS domain of a bacterial phospho-glucose isomerase EC:5.3.1.9 protein which is similar to eukaryote homologues to the extent that the sequence includes the cluster of threonines and serines that forms the sugar phosphate-binding site in conventional PGI. This domain contributes a good proportion of the active catalytic site residues. This PGI uses the same catalytic mechanisms for both glucose ring-opening and isomerisation for the interconversion of glucose 6-phosphate to fructose 6-phosphate [1]. It is associated with family SIS, Pfam:PF01380.

1: A novel phosphoglucose isomerase (PGI)/phosphomannose isomerase from the crenarchaeon Pyrobaculum aerophilum is a member of the PGI superfamily: structural evidence at 1.16-A resolution. Swan MK, Hansen T, Schonheit P, Davies C; J Biol Chem. 2004;279:39838-39845. PMID:15252053