Phosphoglycerate mutase

Proximal Residues Bound To Citrate in Active Site of PGM

3-phospho-D-glycerate wpmp

2,3-Bisphosphoglycerate

2-phospho-D-glycerate wpmp

Phosphoglycerate mutase (PGAM or PGM) is an enzyme that plays a crucial role in the process of glycolysis and gluconeogenesis. This enzyme is involved in the step that interconverts 3-phosphoglycerate (3-PG) and 2-phosphoglycerate (2-PG) during cellular respiration. Phosphoglycerate mutase exists in different isoforms, which are found in various types of tissues in the body, indicating its essential role in energy metabolism across different cell types.

Function

The primary function of phosphoglycerate mutase is to catalyze the transfer of a phosphate group from the 3-position to the 2-position in glycerate phosphate. This reaction is reversible and plays a vital role in both the glycolytic pathway, where glucose is broken down to produce energy, and gluconeogenesis, the process of glucose synthesis. The enzyme's action facilitates the metabolic pathway's progression towards the production of pyruvate in glycolysis or towards the generation of glucose in gluconeogenesis.

Structure

Phosphoglycerate mutase exists mainly in two forms: 1) as a dimeric enzyme which is primarily found in muscle tissues (PGAM1), and 2) as a monomeric form which is more common in non-muscle tissues. The structure of PGAM includes an active site that binds to the substrate (3-phosphoglycerate or 2-phosphoglycerate) and a catalytic site that facilitates the transfer of the phosphate group. The enzyme's activity is dependent on the presence of 2,3-bisphosphoglycerate (2,3-BPG) as a cofactor in the glycolytic pathway.

Isoforms

There are several isoforms of phosphoglycerate mutase, each encoded by different genes and expressed in various tissues. The most well-known isoforms are:

• PGAM1, which is predominantly found in muscle tissue and is involved in rapid energy production during muscle contraction.
• PGAM2, which is expressed in other tissues and plays a role in the regular energy metabolism of cells.

Clinical Significance

Alterations in the activity or expression of phosphoglycerate mutase can have significant implications for human health. Deficiencies in PGAM2, for example, can lead to a metabolic disorder known as glycogen storage disease type X, characterized by muscle cramps and exercise intolerance due to impaired glycolytic flux in muscle cells. Furthermore, changes in PGAM1 expression have been observed in various types of cancer, suggesting that the enzyme could play a role in cancer metabolism and might serve as a potential target for therapeutic intervention.

See Also

• Glycolysis
• Gluconeogenesis
• Enzyme
• Metabolism
• Glycogen storage disease