How many reducing ends are found in one molecule of glucogen?
only one from the staring glucose molecule
What is the building block for glycogen? Where does it come from?
Glucose 1 phosphate. Made by taking glucose and using glucokinase to make glucose 6 phosphate. Then using phosphoglucomutase to make Glucose 6-phosphate
Phosphoglucomutase (substrate and product)
Glucose 6 phosphate --> Glucose 1 phosphate
The molecule that actually is added to the growing glycogen chain is ____________
UDP-glucose (nucleotide bound to glucose)
UDP glucose pyrophosphorylase
adds UDP to glucose 1 Phosphate
Glycogen synthase
makes the alpha 1,4 glycosidic bond on the non-reducing end. Makes amylose
Glycogenin
the seed for glucogen metabolism" A protein primer that acts as a scaphold in glycogen synthesis. Contains the initial glucose monomer that will be built upon one glucose at a time to make glycogen polymer. The glycogen is built from the reducing end/glycogenin end.
How do we add branches to the amylose polymer?
branching enzyme (glycosyl 4:6 transferase) denotes the bond you have to break followed by the bond you have to make. Snip alpha 1-4, then create an alpha 1-6 glycosidic bond.
When does the branching enzyme begin branching?
When the growing amylose chain is at least 11 residues long.
How close can the branch be to each other?
Closest any two branches can be is 4 glucose residues away from each other. Bulky enzyme
Why is branching of glycogen so important?
Increases the rate of glycogen synthesis (more workers can build on the branched ends). Makes it easier to cleave glycogen and free glucose - flight or flight response. You will die if there are no branches (amylose) - kills liver cell.
phosphorylase
break bond by adding P. Glycogenlysis. Analogous of hydroxylase - but with out water.
Glycogen phosporylase
chops off glucose monomer from glycogen by adding P to C1. Makes Glu-1-P. Cofactor is Pyridoxal phosphate (PLP) derived from vitamin B6
Limit dextrins
remaining branch points (4 glucose units long) that can not be digested by glucogen phosphorylase due to 3D shape. These must be broken down or it will cause harm to liver.
Glycogen debranching enzyme
2 functional parts. Like a Swiss army knife. Glycosyl 4:4 transferase = breaks the alpha 1-4 glycosidic bond on branch and transfers it to a free. Amylo alpha 1,6 glucosidase breaks the alpha 1-6 glycosidic bond freeing glucose using water (hydrolysis rxn).
where is glucose 6 phosphatase found?
only found in the liver. Used to cleave the P group from glucose 6-P so that free glucose can be released into the blood