Glycogen Synthesis steps

in glycogen, glucose units are attached by

alpha(1–>4) linear glycosidic

alpha(1–>6) branching glycosidic

step 1 glycogen synthesis ***requiring ATP

glut 2 uptake in liver, pancreas, kidneys

glut 4 uptake in muscle, adipose

glucose phosphorylated to g6p

(glucokinase in liver and hexokinase in muscle)

step 2 slycogen synthesis

isomerization of g6p to g1p via phosphoglucomutase

step 3 glycogen synthesis

g1p and UTP form UDP glucose

need UDP glucose because its activated form and its the substrate/energy for glycogen synthase

coupling of 2 rxns:

transfer of UMP to G1P from UTP (enzyme glucose pyrophosphorylase)

PPi hydrolysis (enzyme inorganic pyrophosphatase)

step 4 glycogen synthesis

glycogenin is a primer protein making glycogen primer 

transfer of glucose from UDP-glucose to Tyr-194 of glycogenin

until 8 glucose units are formed

glycogen synthase uses UDP glucose to add the glucose unit to the non reducing end of an existing glycogen chain forming alpha(1–>4) glycosidic bond

step 5 glycogen synthesis

glycogen branching enzyme will transfer a block of 7 glucose units to a interior site to produce alpha (1–>6) bond which is the branching