The branching enzyme in glycogenesis is called 1,4-alpha-glucan-branching enzyme, also known as brancher enzyme or glycogen-branching enzyme. This enzyme plays a crucial role in the synthesis of glycogen.
The Role of 1,4-alpha-glucan-branching enzyme
The 1,4-alpha-glucan-branching enzyme is essential for creating the highly branched structure of glycogen. Glycogen is a storage form of glucose found mainly in the liver and muscle cells. Without this branching, the glycogen molecule would not be as compact, and its ability to efficiently store and release glucose would be greatly reduced. Here's how it functions:
- Chain Lengthening: Glycogen synthase adds glucose molecules to create a linear chain with alpha-1,4-glycosidic bonds.
- Branch Creation: When a linear chain of glucose is long enough, the branching enzyme transfers a segment of the chain (usually about 6-7 glucose residues) from the existing chain to another point in the glycogen molecule.
- Branch Point: This transfer creates a new alpha-1,6-glycosidic bond, establishing a branch point.
Why Branching Is Important
The highly branched structure of glycogen is advantageous for several reasons:
- Compact Storage: Branching creates a more compact molecule allowing more glucose to be stored in a small space.
- Increased Solubility: Branching makes glycogen more soluble than a linear chain, facilitating efficient storage and release of glucose.
- Rapid Glucose Release: The multitude of branch ends allows for the simultaneous addition or removal of many glucose molecules, leading to faster glucose mobilization when needed for energy.
Summary Table
| Enzyme Name | Other Names | Function | Gene |
|---|---|---|---|
| 1,4-alpha-glucan-branching enzyme | Brancher enzyme, Glycogen-branching enzyme | Creates alpha-1,6-glycosidic branches in glycogen, crucial for its structure. | GBE1 |
The gene that encodes for this enzyme in humans is GBE1.
