Structural highlights
Function[GLMS_ECOLI] Catalyzes the first step in hexosamine metabolism, converting fructose-6P into glucosamine-6P using glutamine as a nitrogen source. Publication Abstract from PubMedGlucosamine-6P synthase catalyzes the synthesis of glucosamine-6P from fructose-6P and glutamine and uses a channel to transfer ammonia from its glutaminase to its synthase active site. X-ray structures of glucosamine-6P synthase have been determined at 2.05 Angstroms resolution in the presence of fructose-6P and at 2.35 Angstroms resolution in the presence of fructose-6P and 6-diazo-5-oxo-L-norleucine, a glutamine affinity analog that covalently modifies the N-terminal catalytic cysteine, therefore mimicking the gamma-glutamyl-thioester intermediate formed during hydrolysis of glutamine. The fixation of the glutamine analog activates the enzyme through several major structural changes: 1) the closure of a loop to shield the glutaminase site accompanied by significant domain hinging, 2) the activation of catalytic residues involved in glutamine hydrolysis, i.e. the alpha-amino group of Cys-1 and Asn-98 that is positioned to form the oxyanion hole, and 3) a 75 degrees rotation of the Trp-74 indole group that opens the ammonia channel. Glutamine binding opens the ammonia channel and activates glucosamine-6P synthase.,Mouilleron S, Badet-Denisot MA, Golinelli-Pimpaneau B J Biol Chem. 2006 Feb 17;281(7):4404-12. Epub 2005 Dec 9. PMID:16339762[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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