glycogenolysis - Glycogenolysis . Glycogen Metabolism...

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Unformatted text preview: Glycogenolysis . Glycogen Metabolism Glycogen Degradation Reactions and Enzymes Sites of Storage and Use Regulation of Glycogen Metabolism- Mechanisms of Regulation Hormonal Control of Enzymes Coordinate Regulation of Synthesis and Degradation I mportance of Glycogen Metabolism and I ntersection with Hexose Metabolism- Glycogen Storage Diseases Glycogen Structure Linkages all a; 1->4 chains and 1->6 branches Branches every 8-12 residues allow compact, less fibrillar structure and high number of non-reducing ends for rapid access to large number of glucose residues Most Glycogen is Stored in Liver and Muscle Muscle Glycogen Stored as Particles- one glycogenin per particle Liver Glycogen Stored as Particles- appear as rosettes of particles, but still only one glycogenin per particle Liver - 6-8% glycogen, wet weight Muscle - 1-2% glycogen, wet weight Glycogen plays different roles in liver and muscle Liver supplies tissues with Glc from glycogen during fasting In muscle, conversion of glycogen to Glc is important during strenuous exercise, and conversion of Glc to glycogen plays important role in lowering blood Glc after feeding Liver glycogen stores are partially depleted, even during short fasts Depletion of Liver Glycogen over 24 h Two major enzymes participate in all glycogen degradation: Glycogen phosphor ylase and Glycogen debr anching enzyme Glycogen phosphorylase removes most glucose residues as Glc-1-P Glycogen phosphorylase, a homodimer, possesses phosphorolytic activity toward -1->4 linkages Degradation by phosphorylase is from non- reducing ends, releasing successive Glc-1-P residues, BUT only to within 4 residues of a branchpoint Molecules left after complete phosphorylase digestion of glycogen are Limit Dextrins Non-reducing ends Reducing end Glycogen Debranching Enzyme accesses branchpoints and residues close to branchpoints The Debranching Enzyme accomplishes this using two different enzyme activities on the same polypeptide; - 1,4->1,4 Glucan transferase and - 1,6 Glucosidase 1 . 1 ....
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This note was uploaded on 10/07/2010 for the course DBT 446 taught by Professor Dd during the Spring '10 term at Indian Institute of Technology, Guwahati.

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glycogenolysis - Glycogenolysis . Glycogen Metabolism...

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