Lecture #70

• homo-polymer of glucose
• rapidly mobilized storage form of glucose

maintain glucose homeostasis

• main energy source:brain and RBC
• modify lips 
• for PPP

• meals
• glycogen and fasting 
• GNG during prolonged fasting

• in the cytosol  in cytosolic granuels 
• liver
• skeletal muscle
• kidney

• glycogen has many branches
• a-1,4 linkages 9 main chain) with a-1,6 at the branching sites

• the hydroxy on the anomeric is linked to the C4
• a carbon is point downward alpha  mean that the carbon is point downwards

• without the aldhyde group 
• this is where glucoses are added and removed

the end of the glycogen with the aldehyde

Glucose>G6P9 ( via hexokinase or glucokinase ) >G1P ( via phosphoglucomustase)>UDPG (via UDG-glucose pyrophosphorylase ) >glycogen ( via transferase, synthase  and glycogen primer)

Glycogen> Glucose ( via glycogen phosphorylase + debranching enzyme)> G1P > G6P ( via phosphoglucomutase) >Glucose ( G6Phosphatase)

glycogenesis

it activates it so that it can link to other glucose  to make glycogen

Glucose 6 phosphate > G1P(via phosphoglucomutase)>UDP glucose ( via UDP glucose pyrophosphorylase)> Glycogen  (via glycogen synthase)

• oligosaccharide primer
• glycogenin

through glucose autoglycosylation activity a tyrosine residue is added.

enzyme and scaffold, extending the carbohydrate chain up to 8 glucose oligomer using UDP-glucose donor

it removes a 6 to 8 oligomer from non reducing end and attached it by a-1,6 linakage ( at least 4 residues from a branch point )

• more soluble 
• creates a large # of non-reducing ends which increases the rate or synthesis and degradation

transfer glucose from UDP glucose to the non reducing end

glycogenolysis

liver can push out glucose but muscles cannot.

1-3% of glycogen is continuosly degraded by the lysosomal enzyme a-1,4 glucosidase

• Type II glycogen storage disease
• deficiency of the lysosomal alpha- 1,4glucosidase 
• causing the build up of glycogen and impariment of normal functioning of organ especially heart

trigger glycogen breakdown

phosphatatase

Kinase

glucose cannot be released in the blood  and accumulates in liver and kidney

• type Ia  is deficiency in Glucose 6 phosphatase 
• Type Ib is deficency in glucose 6 phosphate translocase

the deb ranching enzyme is defective

fructokinase and aldolase B triose kinase  which results in glyceraldehyde 3 phosphate.

fructose kinase deficency

aldolas B deficency resuling in decrease in cellular interstital phosphate and ATP

an alcohol form of glucose

this phosporylates the phosphorylase kinase

aldose reductase