26. Glycogen Synthase

Glycogen Metabolism?

Proceso de almacenar y romper glucosa en el cuerpo

Where is glycogen mainly stored?

Skeletal muscle and liver

Skeletal muscle

fuel reserve for ATP due to contraction

Liver

maintains blood glucose levels

Glycogen

Polimero de Glucosas

Los polímeros de glucosas están unidos por?

a 1-4 glycosidic bonds

a 1-6 glycosidic bonds

Glycogen structure?

Granulos esferoides intracelulares

Where does glycogen synthesis occur?

In the cytosol, requiring ATP/UTP.

Glycogen to glucose in muscles

Doesn't occur because glucose-6-phosphatase is absent (dephosphorylation can't happen).

Muscle glycogen is depleted in short periods of fasting?

No

How is Muscle glycogen depleted in prolonged fasting (18h)?

Moderately depleted

alpha-1,4 linkage

primary glycosidic bond

alpha-1,6 linkage

branch created after 8 to 10 glycosyl residue.

UDP-Glucose pyrophospohrylase

activates glycosil units

In glycogen synthesis, Glucose 6-P is converted into?

Glucose 1-P

What enzyme is use to form Glucose 1-P

Phosphoglucomutase

In glycogen synthesis, Glucose 1-P is converted into?

UDP-Glucose

UDP- Glucose

Precursor Inmediato de glycogen synthesis. Dona glucógenos para que la cadena crezca

What enzyme is use to form UDP-Glucose?

UDP-Glucose Pyrophosphorylase

In glycogen synthesis, UDP-Glucose is converted into?

Glycogen

What enzyme is use to form Glycogen?

Glycogen Synthase

Glycogen Synthase?

Rate Limiting Enzyme

Glycogen Synthase es responsable de que?

De los a-1,4 linkages, pero solo añade glucosas a cadenas existentes.

Que pasa cuando Glycogen Syntase no tienen una cadena existente para añadir la glucosa?

UDP-Glucose se degrada, eliminando el UDP y glucosa sirviendo como el primer fragmento. Glycogenin

Que pasa cuando hay 11 glucosas de largo o mas?

Las branching enzymes van a transferir glucosas a otra otra cadena formando 1,6 linkages

Cuales son las branching enzymes?

Glucosyl 4:6 transferasa

Cuantos glucoses las branching enzymes transfieren?

5-8

Nonreducing ends?

Accesible branches of the glycogen molecule

increase in non reducing ends?

accelerates the rates at which glycogen synthesis and degradation can occur and increases solubility.

Degradation of Glycogen: Glycogen converts into?

Glucose-1-phosphate

Degradation of Glycogen: What enzyme is use to form Glycogen?

Glycogen Phosphorylase

Glycogen phosphorylase?

Rate limiting Enzyme. Has a cofactor called Pyridoxal Phosphate

Glycogen Phosphorylase + pyridoxal phosphatase?

Degrada glucógeno hasta quedan con 4 unidades

Limit Dextrin

Estructura de 4 unidades de la degradación de glucógeno

Degradation of Glycogen: Los branches de la estructura son removidos por?

Debranching Enzymes

Debranching Enzymes?

Glucosyl 4:4 transferase, Amylo a-1,6-glucosidase

Degradation of Glycogen: Glucose-1-P coverts into?

Glucose 6-P

Degradation of Glycogen: What enzyme is use to produce Glucose-6-P?

Phosphoglucomutase

Enzimas reguladas?

Glycogen Synthase y Glycogen Phosphorylase

Positive and negative inhibitions of Glycogen Synthase?

Negative: Glucagon, Epinephrine, Fosforilacion por Kinase cAMP dependent

Positive: Insulin, High energy levels

Positive and negative inhibitions of Glycogen Phosphorylase?

Negative: Insulin

Positive: Glucagon, Epinephrine, Fosforilación por Kinase cAMP dependent, High energy levels

Pompe's disease (type II)

deficiency in lysosomal α-1,4-glucosidase (acid maltase), leads to accumulation of glycogen in vacuoles.

Endoplasmic reticulum

Where the conversion of glucose 6 phosphate to glucose occurs.

McArdle Syndrome (Type V)

Affects skeletal muscle. Glycogen phosphorylase deficiency.

Cori disease (type III)

4:4 transferase and/or 1:6 glucsidase (debranching enzymes) deficiency.

Symptoms of Cori disease (type III)

May have delayed tooth eruption and increased caries risk

GSD IX

Can exhibit oral abnormalities and potentially increased caries.

GSD Ia and Ib

Increased risk of periodontitis, oral ulcers, and bleedingdiathesis