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J Mol Biol. 2001 Nov 9;313(5):1093-102.

Channeling of ammonia in glucosamine-6-phosphate synthase.

Author information

  • 1European Molecular Biology Laboratory, Notkestr. 85, D-22603 Hamburg, Germany. alexey@carb.inst.gov

Abstract

Glucosamine-6-phosphate synthase catalyses the first and rate-limiting step in hexosamine metabolism, converting fructose 6-phosphate into glucosamine 6-phosphate in the presence of glutamine. The crystal structure of the Escherichia coli enzyme reveals the domain organisation of the homodimeric molecule. The 18 A hydrophobic channel sequestered from the solvent connects the glutaminase and isomerase active sites, and provides a means of ammonia transfer from glutamine to sugar phosphate. The C-terminal decapeptide sandwiched between the two domains plays a central role in the transfer. Based on the structure, a mechanism of enzyme action and self-regulation is proposed. It involves large domain movements triggered by substrate binding that lead to the formation of the channel.

Copyright 2001 Academic Press.

PMID:
11700065
[PubMed - indexed for MEDLINE]
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