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  • Title: Channeling of ammonia in glucosamine-6-phosphate synthase.
    Author: Teplyakov A, Obmolova G, Badet B, Badet-Denisot MA.
    Journal: J Mol Biol; 2001 Nov 09; 313(5):1093-102. PubMed ID: 11700065.
    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.
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