Glycogenesis Flashcards
Formation of glycogen
De novo or enlarge
Glycogenesis
Mobilizing glycogen
Dietary glycogen breakdown
Glycogenolysis
Can represent up to 10% of weight of the liver
1-2% of the weight of skeletal muscle
Glycogen
B particle
21 nm in diameter
Consists of up to 55,000 glucose residues
Forms an alpha rosette
Glycogen
Branched polymer of glucose
Stored in cytoplasm as either granules (skeletal muscle) or as clusters of granules (liver)
Has central protein core with polyglucosw chains radiating outward to form a sphere
Glycogen
Glycogen is stored in the
Cytoplasm
Protein in the middle of glycogen
Glycogenin
108 gm in well fed state
Glucose reserve
Amount varies with food intake
Stores last 12 to 24 hours
Liver glycogen
2x the amount in the liver
Fuel reserve of skeletal muscles only
Absence of glucose 6 phosphatase in muscle
Muscle glycogen
Muscle glycogen has no
Glucose 6 Phosphatase
Source of glucose during hypoglycemia
Liver glycogen
Stored as an energy reserve for muscle contraction
Muscle glycogen
White fast twitch muscle fibers employs conversion of glucose to
lactate
Red slow twitch muscle fibers employs glucose in this state
oxidized
Requirements for glycogen formation
Glycogenin
Glycogen synthase
Glycogen branching enzyme
UDP-glucose pyrophosphorylase
Two issues of glycogenesis
Formation of new glycogen particle
Enlargement of existing glycogen particle
Precursor of glycogenesis
Glucose donor
UDP glucose
Uridine Diphosphate Glucose
Glycogen synthesis is through
Polymerizarion of glucose via
Glycogen synthase
Branching enzyme
Core glycogen particle is extended by the
UDP glucose and glycogen synthase
Glycogenesis debranching enzyme
Glucosyl alpha-1,4: alpha-1,5 glucosidase
Regulatory enzyme of Glycogenesis
Glycogen synthase
Synthesis of UDP-Glucose
Formarion of Glycogen Primer
Glycogenesis
Serves as a primer for synthesis of new glycogen particles
Glycogenin
Breakdown of glycogen to glucose
Glycogenolysis
Glycogenolysis is catalyzed by
glycogen phosphorylase
Mobilizing glycogen
Glycogenolysis
Muscle glycogen will not last for an hour
Liver glycogen can be depleted in 12-24 hours
To mobilize glycogen, three enzymes are required
Glycogen phosphorylase
Debranching enzyme
Phosphoglucomutase
GlycoGENESIS major enzymes required
Glycogen synthase
Branching enzyme
The end product of glycogenolysis is
glucose 6-phosphate
Use inorganic phosphate to attack nonreducing ends
Glycogen phosphorylase
Phosphorolysis
Debranching enzymes responsible for
Breaking Alpha 1,4 bonds
Hydrolyzing Alpha 1,6
End product of glycogenolysis
Glucose 6 phosphate
Deficiency of Glucose 6 Phosphate
Cherub
Von Gierke’s
Type I
First boyfriend is usually a jerk
Hypoglycemia Lactic acidosis Hepatomegaly Hyperlipidemia Hyperuricemia Short stature
Skin xanthoma
Fatty liver
Glucose-6-Phosphatase Deficiency
Von Gierke’s
Acid maltase deficiency
Alpha 1,4 glucosidase deficiency
Accumulation of glycogen in lysosomes
Pompe’s disease
Muscle hypotonia
Death from heart failure by age 2
Juvenile onset
Muscle distrophy
Adult onset
Pompe’s disease
Debranching Enzyme deficiency
Cori’s disease
Type III
Fasting hypoglycemia
Hepatomegaly
Accumulation of characteristic branched polysaccharide
Polydextrin
Muscle weakness
Type IIIA Debranching Enzyme Deficiency
Cori’s
Fabre’s
Limit dextrinosis
As in Type IIIA but no muscle weakness
Type IIIB Debranching Enzyme
Absence of enzyme amylo 1:4, 1:6 - transglucosidase
Hepatosplenomegaly
Accumulation of polysaccharide with few branching points; dearh from heart or liver failure before age 5
Anderson disease
ABCD
Andersen Branching
Cori Debranching
Muscle phosphorylase/Myophosphorylase Deficiency
Poor exercise tolerance
Muscle glycogen abnormally high (2.5 - 4%)
Blood lactate very low after exercise
McArdle Disease
Hepatic Glycogen Phosphorylase Deficiency
Her’s disease
GSD Type IV
Deficiency of Phosphofructokinase
Tarui’s disease
GSD Type IV
Poor exercise tolerance
Muscle glycogen abnormally high
Blood lactate very low after exercise
Also hemolytic anemia
Phosphofructokinase deficiency
Type IV
Tarui’s
