Food Chemistry and Fish in Nutrition ( 2+1)

6.2.3.1 Step 1. Action of phosphorylase

First step is catalyzed by phosphorylase. This enzyme is specific for the phosphorlytic breaking (phosphorolysis; of hydrolysis) or the 1-4 linkages of glycogen to yield glucose 1-phosphate.

                                     Phosphorylase

            Glycogen(C 6 )_n + P i ↔ Glycogen (C 6) _n-1 + Glucose 1- phosphate

 

The terminal glucosyl residues from the outermost chains of the glycogen molecule are removed sequentially until approximately four glucose residues remain on either side of a 1-6 branch.