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-bindi ...
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.
Several aerobic crenarcheaons, including Pyrobaculum aerophilum, contain an isomerase that converts both glucose-6-phosphate and mannose-6-phosphate (G6P and M6P, which are C2 epimers) into fructose-6-phosphate. Most organisms contain only highly specific phosphoglucose and phosphomannose isomerases (PGIs and PMIs), which only accept either glucose or mannose as a substrate.
These dual specificity isomerases share very low sequence identity with 'conventional' PGIs or PMIs, but structure is conserved, especially at the active site, supporting a common mechanism. They belong to the larger PGI superfamily.
Defined by 4 residues: ARG:A-135GLU:A-203LYS:A-298HIS:B-219