So I'm sure that most of you are wondering why Andersen's disease results in so much trouble despite it only affect one enzyme - Glycogen Branching Enzyme (GBE).
So let me show you guys why...
This picture here shows that by breaking down glycogen* using glycogen phosphorylase (GPase), you get Glucose-1-Phosphate (G-1-P_ which is essential for forming Glucose-6-Phosphate (G-6-P) via an enzyme called phosphoglucomutase. I am sure all of you know the purpose of G-6-P which is to form glucose during glycolysis!
Hence without glycogen due to a defect in GBE, the cell is unable to produce G-1-P and hence unable to produce G-6-P. This is a huge problem for the cell as there is now a lack of glucose and an accumulation of polyglucosan bodies (refer to previous blogpost if you're curious!). This is the reason why the liver suffers so much in Andersen's disease :(
For those of you curious about how G-1-P is converted to G-6-P, it's actually via phosphorylation of Serine residue (due to it having an -OH or hydroxyl group) and it giving away a phosphate group on the other end of the residue (from Carbon-1). Thus it "switches" from G-1-P to G-6-P.
*Glycogen contains alpha-1,4 & alpha-1,6 glycosidic linkages in its structure. The former can be broken down by GPase but the latter requires a debranching enzyme to break the linkage and in the process of doing so, produce glucose as well!
It's been a really fun & great journey to blog about Andersen's disease and raising awareness by this project but all good things come to an end!
Thank you all for reading the long posts
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