Structural highlights
Function[PYGM_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. Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedIminosugars DAB (5), isofagomine (9), and several N-substituted derivatives have been identified as potent inhibitors of liver glycogen phosphorylase a (IC(50) = 0.4-1.2 microM) and of basal and glucagon-stimulated glycogenolysis (IC(50) = 1-3 microM). The X-ray structures of 5, 9, and its N-3-phenylpropyl analogue 8 in complex with rabbit muscle glycogen phosphorylase (GPb) shows that iminosugars bind tightly at the catalytic site in the presence of the substrate phosphate and induce conformational changes that characterize the R-state conformation of the enzyme. Charged nitrogen N1 is within hydrogen-bonding distance with the carbonyl oxygen of His377 (5) and in ionic contact with the substrate phosphate oxygen (8 and 9). Our findings suggest that the inhibitors function as oxocarbenium ion transition-state analogues. The conformational change to the R state provides an explanation for previous findings that 5, unlike inhibitors that favor the T state, promotes phosphorylation of GPb in hepatocytes with sequential inactivation of glycogen synthase. Iminosugars as potential inhibitors of glycogenolysis: structural insights into the molecular basis of glycogen phosphorylase inhibition.,Oikonomakos NG, Tiraidis C, Leonidas DD, Zographos SE, Kristiansen M, Jessen CU, Norskov-Lauritsen L, Agius L J Med Chem. 2006 Sep 21;49(19):5687-701. PMID:16970395[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
| ||||||||||||||||||||||||
This page was last modified 14:42, 29 December 2021.