glycogen link as
α-(1,4) glycosidic linkage
There is only one reducing end of glycogen;
it is “capped” by a protein called _____
glycogenin
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glycogen link as
α-(1,4) glycosidic linkage
There is only one reducing end of glycogen;
it is “capped” by a protein called _____
glycogenin
Glycogen is a ____ process
anabolic
glycogenin is connected to amino acid
Tyrosine (Tyr,Y)
Glycogenesis Step 1
Conversion of glucose 6-phosphate to glucose 1-phosphate, Phosphoglucomutase
Glycogenesis Step 2
Synthesis of UDP-glucose, UDP-glucose pyrophosphorylase
Glycogenesis Step 3
Synthesis of an initiating primer, Glycogenin
Glycogenesis Step 4
Chain elongation, Glycogen synthase
Glycogenesis Step 5
Formation of branches, (creation of 1,6 branches and extension of 1,4 branched chain), 4:6 transferase (branching enzyme)
The breakdown of glycogen to release glucose 1-phosphate and α-D-glucose
Glycogenolysis
Glycogenolysis is a _____ pathway
catabolic
Glycogenolysis Step 1
Shortening of glycosidic chains, Glycogen phosphorylase
Glycogenolysis Step 2
De-branching (move 3 residues), 4:4 transferase (debranching enzyme #1)
Glycogenolysis Step 3
De-branching (remove 1 glucose), 1:6 glucosidase (debranching enzyme #2)
Glycogenolysis Step 4
Conversion of glucose 1-phosphate to glucose 6-phosphate, Phosphoglucomutase
Step 1: Shortening of glycosidic chains
Enzyme continues until four glucosyl units remain from the branch point
This four unit “stump” is called _______
limit dextrin
Step 2: Debranching (remove 3 units)
_____ initiates the action of a debranching enzyme
Limit dextrin
Glycogenolysis: Step 3: Debranching (remove 1 glucose)
________ is used again for degradation if needed
Glycogen phosphorylase
Glycogenolysis: Conversion of glucose 1-phosphate to glucose 6-phosphate
Glucose 6-phosphate is transported to the ER by glucose 6-phosphate _____
translocase
Glycogenolysis: Conversion of glucose 1-phosphate to glucose 6-phosphate
In the ER, glucose 6-phosphate is converted to glucose by glucose 6 - _____
phosphatase
Muscle lacks _______
glucose 6-phosphatase
Glycogen breakdown:
________ works on non-reducing ends until it reaches four residues from an (16) branch point.
Glycogen phosphorylase
Glycogen breakdown: ______ transfers a block of three residues to the non-reducing end of the chain
Debranching enzyme #1
Glycogen breakdown: _______ cleaves the single remaining (16)-linked glucose, which becomes a free glucose unit (i.e., NOT glucose-1-phosphate).
Debranching enzyme #2
In the liver
Well fed state: ______ accelerates
glycogenesis
In the liver
Fasting state: ______ accelerates
glycogenolysis
In the muscle
Active exercise: _______ accelerates
glycogenolysis
In the muscle
At rest: _____ accelerates
glycogenesis
_____ and ______ are hormonally regulated by insulin, glucagon and epinephrine (aka adrenaline)
Glycogen phosphorylase and glycogen synthase
Glycogen phosphorylase and glycogen synthase are hormonally regulated by_______ (aka adrenaline)
insulin, glucagon and epinephrine
____ generally opposes the effects of glucagon and epinephrine
Insulin
____ favors glycogen synthesis
Insulin
Glucagon and epinephrine favor glycogen _____
breakdown
Insulin binds to a receptor and activates a _____
tyrosine kinase
Activated Protein Phosphatase-1 (PP-1) activates ______
Leads to glycogen synthesis
glycogen synthase
Activated Protein Phosphatase-1 (PP-1) inhibits ______
Phosphorylase kinase activates glycogen phosphorylase
Inhibition of phosphorylase kinase thus prevents the breakdown of glycogen
Indirect inhibition of glycogen phosphorylase
phosphorylase kinase
Epinephrine or glucagon activates ____
catalyzes the generation of cyclic AMP (cAMP)
cAMP activates a cAMP-dependent protein kinase
Higher the levels of cAMP, greater the number of activated protein kinase molecules\
cAMP-dependent protein kinase phosphorylates both glycogen synthase and glycogen phosphorylase
Glycogen synthase becomes inactive; glycogen synthesis stops
Glycogen phosphorylase becomes active; glycogen breakdown is favored
adenylyl cyclase