What are the three steps in glycogen degradation and what...

Key Concepts

Debranching Enzyme

The debranching enzyme plays a crucial role in remodeling the glycogen molecule during degradation. It has two activities: a transferase activity that relocates a block of three glucose residues from a branching point to an outer chain, and a glucosidase activity that removes the remaining single glucose residue linked by an ?-1,6 bond at the branch point, thereby facilitating complete glycogen breakdown.

Phosphoglucomutase

Phosphoglucomutase is the enzyme responsible for converting glucose 1-phosphate, obtained from glycogen phosphorylase activity, into glucose 6-phosphate. This conversion is essential as it prepares the glucose molecule for entry into glycolysis or other metabolic pathways, thereby integrating glycogen degradation with cellular energy metabolism.

Glycogenolysis

Glycogenolysis is the metabolic process of breaking down glycogen into its constituent glucose units. It is a critical pathway that allows the body to mobilize stored energy when needed, converting glycogen into forms that can be readily used in glycolysis and energy production.

Glycogen Phosphorylase

Glycogen phosphorylase is the key enzyme that catalyzes the first step in glycogen degradation. It cleaves glucose residues from the nonreducing ends of the glycogen molecule by adding inorganic phosphate, producing glucose 1-phosphate. This enzyme is regulated to meet the energy demands of the cell.

Transcript

0:00 Okay.

00:02 So for step number one of glycogen degradation, so what enzymes would we need for step number one? well, we would need for the first step.

00:20 So let's do it this way.

00:23 So glycogen, right, needs to be broken down somewhat by glycogen phosphorylase.

00:37 So let's write this in green.

00:41 Glycogen phosphorylase.

00:50 And what is going to be taken from glycogen here? we're looking for a phosphate group.

00:57 So glucose 1 phosphate is what we're hoping to get from glycogen.

01:05 So it's not really, it's not that glycogen, i know this is confusing the way that i'm writing it.

01:09 It's not that i'm saying.

01:10 Saying that glycogen goes through some chemical reaction with glycogen phosphorylase as a catalyst to create glucose 1 phosphate.

01:19 That's not what this is showing.

01:21 This is supposed to show that glycogen, you need glycogen, and you've got to take a piece out of glycogen through glycogen phosphorylase to get glucose 1 phosphate from glycogen.

01:35 So you're just like snipping it off, kind of, is the way that i like to think of it.

01:41 So you're releasing it.

01:43 They call it releasing.

01:44 You're releasing glucose 1 phosphate.

01:47 That's what we're concerned about here.

01:49 Step 2 then would be we need to create glucose 6 phosphate.

01:57 We only have glucose 1 phosphate, so we need to create glucose 1 phosphate.

02:03 So i'll put number 2 here.

02:08 So we have glucose 1.

02:20 Phosphate and we need to create glucose six.

02:30 Let's do that way, phosphate...