3mt8
Glycogen phosphorylase complexed with 4-chlorobenzaldehyde-4-(beta-D-glucopyranosyl)-thiosemicarbazone
Structural highlights
FunctionPYGM_RABIT Phosphorylase is an important allosteric enzyme in carbohydrate metabolism. Enzymes from different sources differ in their regulatory mechanisms and in their natural substrates. However, all known phosphorylases share catalytic and structural properties. Publication Abstract from PubMedGlycogen phosphorylase (GP) is a promising target for the treatment of type 2 diabetes. In the process of structure based drug design for GP, a group of 15 aromatic aldehyde 4-(beta-d-glucopyranosyl)thiosemicarbazones have been synthesized and evaluated as inhibitors of rabbit muscle glycogen phosphorylase b (GPb) by kinetic studies. These compounds are competitive inhibitors of GPb with respect to alpha-d-glucose-1-phosphate with IC(50) values ranging from 5.7 to 524.3muM. In order to elucidate the structural basis of their inhibition, the crystal structures of these compounds in complex with GPb at 1.95-2.23A resolution were determined. The complex structures reveal that the inhibitors are accommodated at the catalytic site with the glucopyranosyl moiety at approximately the same position as alpha-d-glucose and stabilize the T conformation of the 280s loop. The thiosemicarbazone part of the studied glucosyl thiosemicarbazones possess a moiety derived from substituted benzaldehydes with NO(2), F, Cl, Br, OH, OMe, CF(3), or Me at the ortho-, meta- or para-position of the aromatic ring as well as a moiety derived from 4-pyridinecarboxaldehyde. These fit tightly into the beta-pocket, a side channel from the catalytic site with no access to the bulk solvent. The differences in their inhibitory potency can be interpreted in terms of variations in the interactions of the aldehyde-derived moiety with protein residues in the beta-pocket. In addition, 14 out of the 15 studied inhibitors were found bound at the new allosteric site of the enzyme. The binding of beta-d-glucopyranosyl-thiosemicarbazone derivatives to glycogen phosphorylase: A new class of inhibitors.,Alexacou KM, Tenchiu Deleanu AC, Chrysina ED, Charavgi MD, Kostas ID, Zographos SE, Oikonomakos NG, Leonidas DD Bioorg Med Chem. 2010 Nov 15;18(22):7911-22. Epub 2010 Sep 22. PMID:20947361[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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