Kinetic and crystallographic studies on 2-(beta-D-glucopyranosyl)-5-methyl-1, 3, 4-oxadiazole, -benzothiazole, and -benzimidazole, inhibitors of muscle glycogen phosphorylase b. Evidence for a new binding site.
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 beta-D-glucopyranose, 2-(beta-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) muM, 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 A; GPb-benzothiazole, 2.10 A; GPb-benzimidazole, 1.93 A). 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 (approximately 32 A) from the other binding sites, that is mostly dominated by the nonpolar groups of Phe202, Tyr203, Val221, and Phe252.
Chrysina
Evangelia D
ED
Institute of Organic and Pharmaceutical Chemistry, The National Hellenic Research Foundation, 48 Vassileos Constantinou Avenue, 116 35 Athens, Greece.
Kosmopoulou
Magda N
MN
Tiraidis
Constantinos
C
Kardakaris
Rozina
R
Bischler
Nicolas
N
Leonidas
Demetres D
DD
Hadady
Zsuzsa
Z
Somsak
Laszlo
L
Docsa
Tibor
T
Gergely
Pal
P
Oikonomakos
Nikos G
NG
D001562:Benzimidazoles / Q000737:chemistry* / Q000378:metabolism; D001665:Binding Sites; D018360:Crystallography, X-Ray; D004791:Enzyme Inhibitors / Q000737:chemistry* / Q000378:metabolism; D005960:Glucosides / Q000737:chemistry* / Q000378:metabolism; D007700:Kinetics; D008958:Models, Molecular; D010069:Oxadiazoles / Q000737:chemistry* / Q000378:metabolism; D010763:Phosphorylase b / Q000737:chemistry* / Q000378:metabolism; D013844:Thiazoles / Q000737:chemistry* / Q000378:metabolism
C502367:2-glucopyranosyl-5-methyl-1,3,4-oxadiazole; C502368:2-glucopyranosyl-5-methylbenzimidazole; C502369:2-glucopyranosyl-5-methylbenzothiazole; D001562:Benzimidazoles; D004791:Enzyme Inhibitors; D005960:Glucosides; D010069:Oxadiazoles; D013844:Thiazoles; D010763:Phosphorylase b
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