Structure & Basics
These are the two types of glycosidic bonds found in a branched glycogen molecule.
What are α(1→4) and α(1→6) linkages?
This "activated" nucleotide sugar is the high-energy building block used by glycogen synthase
UDP-glucose
Binding of these two hormones to G protein-coupled receptors triggers the cAMP-directed pathway for glycogen degradation.
glucagon and epinephrine
This GSD, also known as Type Ia, is caused by a deficiency in glucose 6-phosphatase and leads to severe fasting hypoglycemia.
Von Gierke disease
This protein serves as the essential primer for glycogen synthesis when glycogen stores are totally depleted.
glycogenin
This enzyme is responsible for breaking α(1→4) bonds and creating the α(1→6) bonds that make glycogen a branched polymer.
branching enzyme (or amylo-α(1→4)→α(1→6)-transglucosidase)
Unlike glycogen phosphorylase, the enzyme glycogen synthase is in its inactive form when it is in this chemical state.
phosphorylated
This is the only glycogen storage disease that is also characterized as a lysosomal storage disease.
Pompe disease (Type II)
While muscle glycogen provides energy for contraction, liver glycogen is primarily used for this physiological purpose
maintaining blood glucose concentration (especially during early stages of a fast)
This enzyme requires the coenzyme pyridoxal phosphate (PLP) to cleave glucose residues from the nonreducing ends of glycogen.
glycogen phosphorylase
In muscle, this molecule acts as an allosteric activator of glycogen phosphorylase b during extreme conditions of anoxia and ATP depletion.
AMP
These genetic disorders result from a defect in an enzyme required for either the synthesis or degradation of glycogen
Glycogen Storage Diseases (GSDs
This is the primary product released when glycogen is degraded by glycogen phosphorylase.
glucose 1-phosphate
This cytosolic enzyme catalyzes the reversible interconversion of glucose 1-phosphate and glucose 6-phosphate.
phosphoglucomutase
This calcium-binding protein complex activates hepatic phosphorylase kinase without the need for PKA phosphorylation.
Ca2+-calmodulin complex
In Type Ib GSD, the deficiency is not in the phosphatase enzyme itself, but in this specific translocase
glucose 6-phosphate translocase
In the liver, this specific enzyme is required to convert glucose 6-phosphate into free glucose so it can enter the blood.
glucose 6-phosphatase
This bifunctional enzyme possesses both transferase activity and amylo-α(1→6)-glucosidase activity.
debranching enzyme
This hormone initiates a signal cascade that activates protein phosphatase-1, effectively opposing the effects of glucagon.
insulin
To manage the severe fasting hypoglycemia associated with Von Gierke disease, patients often receive nocturnal gastric infusions of glucose or regular doses of this common, uncooked food product.
uncooked cornstarch