Linear glycogen is bonded at which glucose carbons?
1 (phosporylated) --> 4
Branched glycogen is bonded at which glucose carbons?
1 phosphorylated --> 6
Glc activation for glycogen synthesis
Glycogen synthesis occurs in which direction?
1' to 4'
Branching enzyme name
glycosyl 4-->6 transferase
About how many Glc molecules can be added at a branch point?
~11
What is the benefit of having so many branch points?
more loose ends are available to be cleaved off the glycogen molecule
and
increases solubility (more --OH groups)
Enzyme that cleaves Glc off glycogen
glycogen phosphorylase
Two debranching enzymes
4:6 transferase
**moves all but one sugar**
α-1,6-glucosidase
**frees last Glc**
Two enzymes that control glycogen synthesis/breakdown and regulation
Glucagon and Epi action: fasting hepatocyte
Insulin action: fed hepatocyte
PHOSPHORYLASE
Epi action: fasting skeletal muscle
PHOSPHORYLASE
Insulin action: fed skeletal muscle
GSD 0
Glycogen synthase deficiency
GSD I (van Gierke disease)
Glucose-6-phosphatase deficiency
(cannot remove Glc from liver)
GSD III (Cori disease)
1,6-glucosidase activity deficincy
(cannot remove single sugar)
GSD IV
4:6-transferase defiency
fatal
GSD V (McArdle disease)
Muscle glycogen phosphorylase deficiency
-->exercise intolerance