Question

14. Glycogen catabolism is initiated by the action of:

A. starch phosphatase

B. hexokinase and maltase

C. α-amylase and α-(l, 6)-glucosidase (debranching enzyme)

D. phosphofructokinase

Answer 1

Ans. (C) α-amylase and α-(l, 6)-glucosidase (debranching enzyme)

Catabolism is a process of breaking down of molecules into its smaller unit. Glycogen catabolism is initiated by the action of the enzyme phosphorylse and cleaving the bond linking a terminal glucose residue to a glycogen branch by substitution of a phosphoryl group for the α[1→4] linkage. The α-amylase can hydrolyze a glycosidic linkage anywhere along the chain to produce glucose and maltose. Than after the breakdown of glycogen to glucose-1-phosphate, Glucose-1-phosphate is converted to glucose-6-phosphate by using enzyme  phosphoglucomutase. Glycogen debranching enzyme i.e.α-(l, 6)-glucosidase convert alpha(1-6) branches to alpha(1-4) branches, transfer of trisaccharide from 1,6 branch to an adjacent 1,4 branch, leaving a single glucose at the 1,6 branch.