BCM 475 Chapter Notes - Chapter 21: Glycogen Phosphorylase, Carbonium Ion, Pyridoxal Phosphate
Document Summary
Glycogenn + pi glucose 1-phosphate + glycogenn-1. Phosphorolysis - cleaves glycosidic bond between c1 and c4 by adding pi: replaced with a phosphoryl ester bond (both have nearly equal transfer potential, catalyzes removal of glucoses from nonreducing ends (with free oh on c4) Phosphorylase"s goal: to cleave glycogen phosphorolytically rather than hydrolytically to save. Energetic explanation for phosphorolytic cleavage - energetically advantageous. Maintains energy supplies in muscle cells: glucose 1-phosphate cannot exit cell: glucose 1-phosphate glucose 6-phosphate glycolysis. Phosphorolysis proceeds in glycogen breakdown due to high. No transporters exist for glucose 1-phosphate (due to charges; cannot leave) Hydrolytic cleavage would yield glucose; which would need to be phosphorylated using atp: whereas, phosphorolytic cleavage requires no atp. Free glucose must be phosphorylated with 1 atp. Whereas glycogen is phosphorolytically cleaved (saving energy/1 atp) Mechanistic explanation water exclusion from active site of glucose phosphorylase.
