InterPro domain: IPR035490

This entry represents the SIS (Sugar ISomerase) domain 2 found in glucosamine 6-phosphate synthase (GlmS) and fructosamine deglycase FrlB.

GlmS contains a N-terminal glutaminase domain and C-terminal isomerase domain (consisting of two SIS domains) [ 1 ] and catalyzes the first step in hexosamine metabolism, converting fructose 6-phosphate into glucosamine 6-phosphate using glutamine as nitrogen source [ 2 ]. The glutaminase domain hydrolyzes glutamine to glutamate and ammonia. Ammonia is transferred through a channel to the isomerase domain for glucosamine 6-phosphate synthesis. In the absence of glutamine, GlmS catalyzes the isomerization of fructose 6-phosphate into glucose 6- phosphate [ 3 , 4 , 5 ].

FrlB catalyses the conversion of a range of fructosamine 6-phosphates to glucose 6-phosphate and a free amino acid [ 6 ].

1. Involvement of the C terminus in intramolecular nitrogen channeling in glucosamine 6-phosphate synthase: evidence from a 1.6 A crystal structure of the isomerase domain. Structure 6, 1047-55
2. Dynamics of glucosamine-6-phosphate synthase catalysis. Arch. Biochem. Biophys. 505, 1-12
3. Channeling of ammonia in glucosamine-6-phosphate synthase. J. Mol. Biol. 313, 1093-102
4. Glucosamine-6-phosphate synthase--the multi-facets enzyme. Biochim. Biophys. Acta 1597, 173-92
5. The mechanism of sugar phosphate isomerization by glucosamine 6-phosphate synthase. Protein Sci. 8, 596-602
6. Identification of enzymes acting on alpha-glycated amino acids in Bacillus subtilis. FEBS Lett. 577, 469-72