The binding of C5-alkynyl and alkylfurano 2,3-d pyrimidine glucopyranonucleosides to glycogen phosphorylase b: Synthesis, biochemical and biological assessment

C5-alkynyl and allcylfurano[2,3-d]pyrimidine glucopyranonucleosides have been synthesized and studied as inhibitors of glycogen phosphorylase b (GPb). Kinetic experiments have shown that most of these compounds were low micromolar inhibitors of the enzyme. The best inhibitor was 1-(beta-D-glucopyranosyl)-5-ethynyluracil (K-i = 4.7 mu M). Crystallographic analysis of these compounds in complex with GPb revealed that inhibitors with a long C5-alkynyl group exploited interactions with beta-pocket of the active site and induced significant conformational changes of the 280s loop compared to GPb in complex with compounds with a short C5-alkynyl group. The results highlight the importance in the length of the aliphatic groups used to enhance inhibitory potency for the exploitation of the hydrophobic beta-pocket. The best of the inhibitors had also a moderate effect on glycogenolysis in the cellular lever with an IC50 value of 291.4 mu M. (C) 2012 Elsevier Masson SAS. All rights reserved