Glucosamine-6-phosphate deaminase (GNPDA) is an allosteric enzyme that catalyzes the reversible conversion of D-glucosamine-6-phosphate into D-fructose-6-phosphate and ammonium.  GNPDA1 is one of two mammalian glucosamine-6-phosphate deaminases that are thought to have arisen though gene duplication, with the GNPDA2 protein closer in structure and activity to the E. coli enzyme.   GNPDA1 possesses greater affinity for ammonium than either GNPDA2 or the E. coli enzyme suggesting that the forward reaction of D-glucosamine-6-phosphate into D-fructose-6-phosphate and ammonium is catalyzed at a slower rate than GNPDA2.  GNPDA1 is predicted to not cross-react with GNPDA2.