Where is glycogen mainly stored
liver and muscle
Why doesn't muscle directly put glucose into the blood stream?
lacks glucose6phosphotase
What does glycogen break down to?
Glucose1P
How can Glucose1P enter the citric acid cycle?
by being converted to Glucose6P by phosphoglucomutase
What does glc1P react with to make glycogen?
uridine triphosphate to form UDPGlc and pyrophosphate
What catalyzes the formation of UDPGlc?
UDPGlcpyrophosphorylase
function of pyrophosphatase
hydrolyzes pyrophosphate to two phosphates
function of glycogen synthase
catalyzes glycoside bond betwen C1 of UDPGlc and C4 of terminal glucose residue of glycogen
What kind of bond is found in glycogen?
1-4 glycosidic
What happens if there is no existing glycogen available to add onto?
glycogenin, a primer is used as the base
Which end of glycogen is a new residue added to?
the nonreducing outer end of molecule
What will Tanner's score be on Biochem exam 2?
107
When do branches form in glycogen
when the chain is at least 11 residues long
What is the function of branching enzyme?
it transfers part of the 1-4 chain to a neighboring chain forming a 1-6 branch point
What is the minimum residues transferred by branching enzyme?
6 residues
What is the rate limiting step in glycogenolysis?
phosphorylitic cleavage of the 1-4 linkages
What catalyzes the cleavage of 1-4 linkages?
glycogen phosphorylase
What vitamin is needed for the cleavage of 1-4 linkages
B6 pyridoxal 5' phosphate
What is the catalytically active group in pyridoxal phosphate in glycogenolysis?
phosphate group (aldehyde in amino acid metabolism)
What is the purpose of Pi entering glycogenolysis cycle?
phosphorylation
What is kicked off during the reaction with glycogen synthase?
UDP
What phosphorylates UDP in glycogenesis?
ATP via nucleosidediphosphokinase
How many glucose units are removed at a time in glycogenolysis?
one at a time until 4 on either side of a branch
How many are removed once there are only 4 residues on a branch?
3 and added to a different branch
What is the functions of glucan transferase?
transfers a trisaccharide from one branch to another
What is the relationship between glucan transferase and debranching enzyme?
they are separate active sites on the same molecule
What is the function of debranching enzyme?
hydrolyzes the 1-6 bond of the single remaining glucose on that branch
Glucose 6-phosphatase
found in smooth ER (liver and kidney) and allows increase in blood glucose level
Adenylyl cyclase
forms cAMP from ATP
What increases phosphorylationin?
cAMP
insulin's effect on cAMP
deactivated (inhibits)
glucogon epinephrine and norepinephrine effect on cAMP
activated
what hydrolyzes cAMP
phosphodiesterase
Which end is cleaved by phosphodiesterase?
3' end
functional group in cAMP
diester
What reaction inactivates cAMP?
hydrolysis via phosphodiesterase
What does cAMP activate?
kinase
What is the active form of phosphorylase kinase?
a (b is the inactive form)
What is the function of phosphorylase kinase a?
activates phosphorylase
from form b to a
is phosphorylase kinase a phosphorylated or dephosphorylated?
phosphorylated (inactive form is dephosphorylated)
What enzyme form is needed to break glycogen down?
phosphorylase a
What controls phosphorylase a and b?
phosphorylase kinase
what is the secondary signaling agent in phosphorylase kinase cycle?
Ca from calmodulin
What enzyme is inhibited by G6P?
phosphorylase a
how many amino acids in glucagon
29
similarity between phosphorylase and glycogen synthase
both exist in a phosphorylated and nonphosphorylated forms only the action is opposite
What form is the phosphorylated glycogen synthase?
inactive glycogen synthase b