Debranching enzyme

Debranching enzyme is a crucial enzyme involved in the breakdown of glycogen, the primary storage form of glucose in the body. This enzyme plays a significant role in glycogenolysis, the process by which glycogen is broken down into glucose molecules to be used as energy. Debranching enzyme operates by removing branches from the glycogen molecule, which are created during glycogen synthesis. This action is essential for the efficient and complete degradation of glycogen.

Function

The debranching enzyme has two distinct activities: 4-alpha-D-glucanotransferase activity and amylo-1,6-glucosidase activity. The first activity transfers a trisaccharide from one branch to another, while the second activity removes the single glucose molecule that remains at the branch point. These activities are crucial for the mobilization of glucose from glycogen stores, especially during periods of fasting or intense physical activity.

Structure

Debranching enzyme is encoded by the AGL gene in humans. The enzyme is a single polypeptide that is required for the proper degradation of both liver and muscle glycogen. Mutations in the AGL gene can lead to a condition known as Glycogen storage disease type III (GSD III), characterized by an accumulation of abnormally structured glycogen in the body.

Clinical Significance

Glycogen storage disease type III is a genetic disorder resulting from the deficiency of debranching enzyme activity. This condition can lead to various symptoms, including hypoglycemia, muscle weakness, and hepatomegaly. Diagnosis is typically made through biochemical assays and genetic testing to identify mutations in the AGL gene.

See Also

• Glycogenolysis
• Glycogen storage disease
• Glycogen synthase
• Glycogen phosphorylase