1mor
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ISOMERASE DOMAIN OF GLUCOSAMINE 6-PHOSPHATE SYNTHASE COMPLEXED WITH GLUCOSE 6-PHOSPHATE
OverviewOverview
BACKGROUND: Glucosamine 6-phosphate synthase (GlmS) catalyses the first, step in hexosamine metabolism, converting fructose-6P (6 phosphate) into, glucosamine-6P using glutamine as a nitrogen source. GlmS is a bienzyme, complex consisting of two domains that catalyse glutamine hydrolysis and, sugar-phosphate isomerisation, respectively. Knowledge of the, three-dimensional structure of GlmS is essential for understanding the, general principles of catalysis by ketol isomerases and the mechanism of, nitrogen transfer in glutamine amidotransferases. RESULTS: The crystal, structure of the isomerase domain of the Escherichia coli GlmS with the, reaction product, glucosamine-6P, has been determined at 1.57 A, resolution. It is comprised of two topologically identical subdomains, each of which is dominated by a nucleotide-binding motif of a flavodoxin, type. The catalytic site is assembled by dimerisation of the protein., CONCLUSIONS: The isomerase active site of GlmS seems to be the result of, evolution through gene duplication and subsequent dimerisation., Isomerisation of fructose-6P is likely to involve the formation of a, Schiff base with Lys603 of the enzyme, the ring-opening step catalysed by, His504, and the proton transfer from C1 to C2 of the substrate effected by, Glu488. The highly conserved C-terminal fragment of the chain may play a, key role in substrate binding, catalysis and communication with the, glutaminase domain. The corresponding sequence pattern DXPXXLAK[SC]VT (in, single-letter amino-acid code, where X is any amino acid and letters in, brackets indicate that either serine or cysteine may take this position), may be considered as a fingerprint of GlmS.
About this StructureAbout this Structure
1MOR is a Single protein structure of sequence from Escherichia coli with G6P as ligand. Active as Glutamine--fructose-6-phosphate transaminase (isomerizing), with EC number 2.6.1.16 Full crystallographic information is available from OCA.
ReferenceReference
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., Teplyakov A, Obmolova G, Badet-Denisot MA, Badet B, Polikarpov I, Structure. 1998 Aug 15;6(8):1047-55. PMID:9739095
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