Glycogen Metabolism Flashcards
What enzyme is responsible for incorporating glucose molecules into the glycogen chain via α 1,4 linkages?
Glycogen synthase
From what molecule is glucose added to the glycogen chain?
UDP-glucose
Which enzyme is responsible for the interconversion of glucose-6P and glucose-1P?
Phosphoglucomutase
What enzyme is involved in the introduction of α 1,6 branch points into glycogen?
Branching enzyme
What is the primer required to initiate new glycogen synthesis?
Glycogenin
What is glycogenin?
A self glycosylating protein
How does glycogen phosphorylase break α 1,4 bonds?
By phosphorylation
What occurs to the glucose-6P generated from glycogenolysis in muscle?
It enters glycolysis
What occurs to the glucose-6P generated from glycogenolysis in the liver?
It is converted to glucose
How does debranching in glycogenolysis occur?
- Phosphorylase stops cleaving α 1,4 bonds when it is 4 molecules away from a branch point
- Transferase transfers 3 molecules from the branched section to the linear part
- α-1,6-glucosidase cleaves the α 1,6 bond through hydrolysis
How many molecules away from a branch point does glycogen phosphorylase stop cleaving?
4
What enzyme cleaves the α 1,6 bond in glycogenolysis?
α 1,6-glucosidase
What are the key regulatory enzyme of glycogen metabolism?
- Glycogen synthase
- Glycogen phosphorylase
What are the 2 types of control of glycogen metabolism?
- Allosteric
- Hormonal
What allosterically activates glycogen synthase in the liver?
Glucose and glucose-6P
What allosterically inhibits glycogen phosphorylase in the liver?
Glucose and glucose-6P
What activates glycogen phosphorylase in the muscle?
- Ca2+
- AMP
What inhibits glycogen phosphorylase in the muscle?
ATP
What is the effect of insulin on glycogen synthase?
It activates it
What is the effect of insulin on glycogen phosphorylase?
It inhibits it
What is the effect of adrenaline and glucagon on glycogen synthase?
They inhibit it
What is the effect of adrenaline and glucagon on glycogen phosphorylase?
they activate it
How do hormones activate/inhibit the enzymes?
Through changes in phosphorylation of the enzymes
