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Kinetic and crystallographic studies on 2‐(β‐D‐glucopyranosyl)‐5‐methyl‐1, 3, 4‐oxadiazole, ‐benzothiazole, and ‐benzimidazole, inhibitors of muscle glycogen phosphorylase b. Evidence for a new binding site
Author(s) -
Chrysina Evangelia D.,
Kosmopoulou Magda N.,
Tiraidis Constantinos,
Kardakaris Rozina,
Bischler Nicolas,
Leonidas Demetres D.,
Hadady Zsuzsa,
Somsak Laszlo,
Docsa Tibor,
Gergely Pal,
Oikonomakos Nikos G.
Publication year - 2005
Publication title -
protein science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.353
H-Index - 175
eISSN - 1469-896X
pISSN - 0961-8368
DOI - 10.1110/ps.041216105
Subject(s) - benzothiazole , benzimidazole , chemistry , allosteric regulation , stereochemistry , binding site , glycogen phosphorylase , oxadiazole , active site , enzyme , biochemistry , organic chemistry
In an attempt to identify leads that would enable the design of inhibitors with enhanced affinity for glycogen phosphorylase (GP), that might control hyperglycaemia in type 2 diabetes, three new analogs of β‐D‐glucopyranose, 2‐(β‐D‐glucopyranosyl)‐5‐methyl‐1, 3, 4‐oxadiazole, ‐benzothiazole, and ‐benzimidazole were assessed for their potency to inhibit GPb activity. The compounds showed competitive inhibition (with respect to substrate Glc‐1‐P) with K i values of 145.2 (±11.6), 76 (±4.8), and 8.6 (±0.7) μM, respectively. In order to establish the mechanism of this inhibition, crystallographic studies were carried out and the structures of GPb in complex with the three analogs were determined at high resolution (GPb‐methyl‐oxadiazole complex, 1.92 Å; GPb‐benzothiazole, 2.10 Å; GPb‐benzimidazole, 1.93 Å). The complex structures revealed that the inhibitors can be accommodated in the catalytic site of T‐state GPb with very little change of the tertiary structure, and provide a rationalization for understanding variations in potency of the inhibitors. In addition, benzimidazole bound at the new allosteric inhibitor or indole binding site, located at the subunit interface, in the region of the central cavity, and also at a novel binding site, located at the protein surface, far removed (∼ 32 Å) from the other binding sites, that is mostly dominated by the nonpolar groups of Phe202, Tyr203, Val221, and Phe252.