BIOL214 Lecture Notes - Lecture 7: Glycogen Debranching Enzyme, Glycogen Phosphorylase, Glycogen Branching Enzyme
Document Summary
Understand how glycogen is constructed from phosphorylated glucose, and how this is achieved by the enzymes involved. Understand that glycogen synthesis and degradation is regulated by the hormones insulin, epinephrine and glucagon. Glycogen: polymer of a(1 4) linked subunits of glucose, with a(1 6)linked branches, each chain has 12-14 residues, glycogenin acts as seed that allows growth of existing molecule. Why not store monomeric glucose: glycogen is stored in cells at 0. 01nm. Glycogen beta particles: elementary glycogen particles (or granules, often associated with er tubues, consists of, 55000 glucose molecules, 2000 non reducing ends. Requires 4 enzyme activities: one to degrade glycogen glycogen phosphorylase, two to remodel glycogen for further degradation glycogen debranching enzyme, one to convert the breakdown product into a form suitable for further degradation. Step #1: glycogen phosphorylase: catalyses the breakage of a(1 4) linkage between glucose subunits at non reducing end. Step #2: dealing with branchpoints: glycogen phosphorylase acts repeatedly to remove glucose subunits .
