Glycogen Synthesis Flashcards
what is specific about glycogen synthesis?
a glucose residue cannot directly attach to a glycogen branch
what is the first step of glycogen synthesis?
G1P is turned into UDP-glucose
glycogen synthase acts on what molecule?
on the UDP-glucose
name the 3 enzymes used in glycogen synthesis
UDP-glucose phosphorylase, glycogen synthase, glycogen branching enzyme
what is the function of UDP-glucose phosphorylase
it catalysis the rxn of UTP and G1P, to form UDPG and release of PP
where do we get G1P from?
using glycogen phosphorylase to get glucose from glycogen
describe how glycogen synthase works
it needs a primer. This primer is made by GLYCOGENIN, by using UDP-glucose. A glucosyl unit is attached to he non reducing residue of glycogen, by an alpha(1-4)bond.
function of glycogen synthase is inhibited by?
1,5-gluconolactate
what is the price of a glucose molecule being turned to glycogen
the hydrolysis of UTP, which is regenerated by Nucleoside diphosphate kinase
why is the glycogen branching enzyme a thing?
because glycogen synthase can only form alpha 1-4 bonds and not alpha 1-6 bonds
how does the glycogen branching enzyme work?
it breaks the alpha(1-4)bonds and detaches a 7 residue chain with a non reducing residue. It attaches this branch with an alpha (1-6) bond 4 residues away form a pre-existing branch. NOTE that the branch whose alpha 1-4 bond is broken must be at least 11 residues long
glycogen metabolism is under the control of hormones like
insulin, glucagon, epinephrine
adenylate cyclase
ATP to cAMP
phosphorylase kinase structure
calmodulin (gamma subunit), is activated by protein kinase A, Ca2+
