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  • Title: Binding of beta-D-glucopyranosyl bismethoxyphosphoramidate to glycogen phosphorylase b: kinetic and crystallographic studies.
    Author: Chrysina ED, Kosmopoulou MN, Kardakaris R, Bischler N, Leonidas DD, Kannan T, Loganathan D, Oikonomakos NG.
    Journal: Bioorg Med Chem; 2005 Feb 01; 13(3):765-72. PubMed ID: 15653344.
    Abstract:
    In an attempt to identify a new lead molecule that would enable the design of inhibitors with enhanced affinity for glycogen phosphorylase (GP), beta-D-glucopyranosyl bismethoxyphosphoramidate (phosphoramidate), a glucosyl phosphate analogue, was tested for inhibition of the enzyme. Kinetic experiments showed that the compound was a weak competitive inhibitor of rabbit muscle GPb (with respect to alpha-D-glucose-1-phosphate (Glc-1-P)) with a Ki value of 5.9 (+/-0.1) mM. In order to elucidate the structural basis of inhibition, we determined the structure of GPb complexed with the phosphoramidate at 1.83 A resolution. The complex structure reveals that the inhibitor binds at the catalytic site and induces significant conformational changes in the vicinity of this site. In particular, the 280s loop (residues 282-287) shifts 0.4-4.3 A (main-chain atoms) to accommodate the phosphoramidate, but these conformational changes do not lead to increased contacts between the inhibitor and the protein that would improve ligand binding.
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