Glycogen Metabolism Flashcards
Glycogen synthesis steps
- Activation of glucose
- Elongation
- Branching
- Glycogen synthesized
Activation of glucose
Glu
Glu6p
Glu1p
UDP-glu
Elongation
UDPglu give glu to primer of glycogen or glycogenin protein with oligosach chain of 7 glu . Glycogen synthase enzyme play role.
Branching
When gluc chain becomes of 11-12 then 5-6 gluc chain breaks and attaches over the left chain as a branch . Branching enzyme plays role .
Glycogen catabolism steps
- Chain break
2. Debranching
De elongation enzymes
Alpha-1,4-glycosidic bond break by glycogen phosphorylase
Debranching enzyme and process
Debranching enzyme have two roles first of transferase second of glucosidase
On formation of dextrin that is one glu molecules having two branches of 4 glu attached to it transferase play role in transferring the branch to the straight chain leaving only one glu at branch the long chain and glucosidase break the alpha-1,6-glycosidic bond .
Regulation of glycogen metabolism
2 states - phosphorylated and dephosphorylated form
2 enzymes - glycogen synthase & glycogen phosphorylase
2 hormones - insulin & glucagon
Regulation by hormones
Glucagon -> cAMP -> protein kinase -> phosphorylase kinase -> phosphorylation of glycogen synthase(inactivation) & phosphorylation of glycogen phosphorylase (activation)
Insulin take up cAMP so no phosphorylation
Ca+2 role
It activates phosphorylase kinase
Allosteric regulation
Glucose , glu6p, ATP inhibit phosphorylase kinase
Disorders of glycogen storage
Versatile- von gierkes - glu6phosphatase
Player - pompes’ - acid maltase lysosomal
Cory - cori - debranching enzyme
Anderson’s - anderson - branching enzyme
Made -mcardles - muscle phosphorylase
History- her’s- liver phosphorylase enzyme
Glycogen catabolism product in
Glu-6-p as glu-6-phosphorylase enzyme absent there
