BIOC 3300 Chapter Notes - Chapter 18: Glycogen Phosphorylase, Pyridoxal Phosphate, Phosphorolysis
13 Jan 2016
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Document Summary
In the liver and skeletal muscle. (a) glycogen is major energy source for contraction of skeletal muscle (b) in liver glycogen is stored to maintain blood glucose. Phosphorolysis; hydrolysis: enzymes in mobilization of glycogen, glycogen phosphorylase. Catalyses the reaction releasing glucose- 1-p from the non- reducing end of glycogen. Cannot break down 1,6 linkages at branch points. Phosphorylase stops at a point 4 glucose residues away from the branchpoint. Reaction is near equilibrium but high concentration of pi makes forward reaction favoured: debranching enzyme. Glucantransferase activity transfers triglucose from the branchpoint chain to another outer branch. 1,6-glucosidase activity releases glucose from the branchpoint. Products of glycogen breakdown are predominantly glucose-1-p with some glucose (amount depends on number of branchpoints: phosphoglucomutase only in muscle. Converts glucose-1-p to glucose-6-p for entry to glycolysis: glycogen. To keep glucose-6-p in muscle and offer energy by glycolysis for muscle activity. Generate glucose from glucose-6-p for transport in the blood.
