1MOQ: Isomerase Domain Of Glucosamine 6-Phosphate Synthase Complexed With Glucosamine 6-Phosphate

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.
PDB ID: 1MOQDownload
MMDB ID: 56884
PDB Deposition Date: 1997/4/11
Updated in MMDB: 2012/11
Experimental Method:
x-ray diffraction
Resolution: 1.57  Å
Source Organism:
Similar Structures:
Biological Unit for 1MOQ: dimeric; determined by author and by software (PISA,PQS)
Molecular Components in 1MOQ
Label Count Molecule
Proteins (2 molecules)
Glucosamine 6-phosphate Synthase(Gene symbol: glmS)
Molecule annotation
Chemicals (17 molecules)
* Click molecule labels to explore molecular sequence information.

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