Catalyzes the first step in hexosamine metabolism, converting fructose-6P into glucosamine-6P using glutamine as a nitrogen source. D-fructose 6-phosphate + L-glutamine = D-glucosamine 6-phosphate + L-glutamate Homodimer. Constitutively expressed, part of the cdaA-cdaR-glmM-glmS operon (PubMed:23192352).