AgaS-like protein. AgaS contains a SIS (Sugar ISomerase) domain which is found in many phosphosugar isomerases and phosphosugar binding proteins. AgaS is a putative isomerase in Escherichia coli. It is similar to the glucosamine-6-phosphate synthases (GlmS) which catalyzes the first step in hexosamine metabolism, converting fructose 6-phosphate into glucosamine 6-phosphate using glutamine as nitrogen source.