Glycogenolysis Pathway

Notes

Overview

Glycogen → Glucose-1-phosphate → Glucose-6-phosphate

Step 1: Glycogen → Glucose-1-phosphate

This targets non-reducing ends

ENZYME: Glycogen Phosphorylase

I think of this guy like a pac man, where he goes in and chews off each glucose molecule in the chain. 

It stops 4 glucose from a branch due to a steric issue! The enzyme cannot sterically fit between how close the glucose molecules are at that point. 

Step 2: 

ENZYME: Debranching Enzyme

Of the multiple units, this debranching enzyme utilizes the first subunit, which is a transferase to move 3 glucose next to the branched one. 

Step 3: *Makes glucose, does not proceed to step four* 

ENZYME: Debranching Enzyme 

The second subunit,  ɑ-1,6 glucosidase, is utilized.

It cleaves off the ɑ-1,6 bond by hydrolysis.

• This makes it so that the branched glucose left behind is removed as glucose and is not converted from glucose-1-phosphate to glucose-6-phosphate. 

Instead of forming glucose-1-phosphate it makes glucose due to it being a hydrolysis break

Step 4: Glucose-1-phosphate → Glucose-6-phosphate

ENZYME: Phosphoglucomutase

This converts glucose-1-phosphate to glucose-6-phosphate