Glycogen Debranching Enzyme Functions and Mechanism

The video tutorial explains the mechanisms of glycogen catabolism, focusing on the roles of glycogen phosphorylase and glycogen debranching enzyme. Glycogen phosphorylase removes terminal glucose units as glucose-1-phosphate, while the debranching enzyme, a hydrolase, uses water to release simple glucose. The debranching enzyme has transferase and glucosidase activities, crucial for processing branches with four glucose units. The tutorial also covers the molecular mechanism of the debranching enzyme, highlighting the differences between the two enzymes in terms of their products and processes.

What is the primary difference between glycogen phosphorylase and glycogen debranching enzyme?

• Glycogen phosphorylase uses water, while glycogen debranching enzyme uses phosphate.

• Glycogen phosphorylase has transferase activity, while glycogen debranching enzyme does not.

• Glycogen phosphorylase removes glucose units as glucose one phosphate, while glycogen debranching enzyme removes them as simple glucose.

• Glycogen phosphorylase can act on branches shorter than four glucose units, while glycogen debranching enzyme cannot.

What activity does the glycogen debranching enzyme exhibit when dealing with a branch of four glucose units?

• It phosphorylates the terminal glucose unit.

• It removes all four glucose units as glucose one phosphate.

• It transfers the terminal three glucose units to a nearby chain.

• It converts the branch into a single glucose unit.

Why can't glycogen phosphorylase continue its action on branches shorter than five glucose units?

• It can only act on branches longer than five glucose units.

• It is inhibited by the presence of glycogen debranching enzyme.

• It lacks the necessary enzyme activity.

• It requires a minimum of five glucose units to function.

What is the role of water in the glycogen debranching enzyme's mechanism?

• Water inhibits the enzyme's activity.

• Water is not involved in the mechanism.

• Water phosphorylates the glucose unit.

• Water acts as a nucleophile to cleave the bond.

What is the final product released by the glycogen debranching enzyme?

• Glucose six phosphate

• Glucose one phosphate

• Fructose

• Simple glucose

How does the glycogen debranching enzyme differ from glycogen phosphorylase in terms of the product formed?

• It forms glucose six phosphate directly.

• It forms simple glucose instead of glucose one phosphate.

• It forms glucose one phosphate instead of simple glucose.

• It forms fructose instead of glucose.

What must happen to the glucose released by the glycogen debranching enzyme before it can enter glycolysis?

• It must be converted to fructose.

• It must be phosphorylated by hexokinase to form glucose six phosphate.

• It must be dephosphorylated.

• It must be converted to glucose one phosphate.