Aminotransferases

Definition

Aminotransferases, also known as transaminases, are a class of enzymes that catalyze the transfer of amino groups from one molecule to another. These enzymes play a crucial role in the metabolism of amino acids and the regulation of nitrogen balance within the body.

5 Must Know Facts For Your Next Test

1. Aminotransferases play a key role in the catabolism of proteins by catalyzing the deamination of amino acids, a process that generates ammonia and alpha-keto acids.
2. The two most commonly measured aminotransferases in clinical settings are alanine aminotransferase (ALT) and aspartate aminotransferase (AST), which are used as biomarkers for liver function.
3. Aminotransferases require pyridoxal phosphate, a derivative of vitamin B6, as a cofactor to facilitate the transfer of amino groups.
4. Elevated levels of aminotransferases in the blood can indicate liver damage or dysfunction, as these enzymes are released into the bloodstream when liver cells are injured.
5. Aminotransferases are also involved in the biosynthesis of non-essential amino acids, such as alanine and aspartate, through the process of transamination.

Review Questions

• Explain the role of aminotransferases in the catabolism of proteins and the generation of ammonia.
  • Aminotransferases play a crucial role in the catabolism of proteins by catalyzing the deamination of amino acids. This process involves the removal of the amino group from an amino acid, resulting in the formation of an alpha-keto acid and the release of ammonia. The generated ammonia can then be converted to urea in the liver and excreted from the body, thereby maintaining nitrogen balance and preventing the buildup of toxic levels of ammonia in the bloodstream.
• Describe the importance of aminotransferases as biomarkers for liver function and the significance of elevated levels in the blood.
  • The two most commonly measured aminotransferases, alanine aminotransferase (ALT) and aspartate aminotransferase (AST), are widely used as biomarkers for liver function. When liver cells are damaged or dysfunctional, these enzymes are released into the bloodstream, leading to elevated levels that can be detected through blood tests. Monitoring the levels of aminotransferases in the blood provides valuable information about the health and integrity of the liver, allowing for the early detection and diagnosis of liver-related disorders, such as hepatitis, cirrhosis, or liver injury.
• Explain the role of coenzymes, specifically pyridoxal phosphate, in the catalytic activity of aminotransferases and the significance of this relationship.
  • Aminotransferases require the coenzyme pyridoxal phosphate, a derivative of vitamin B6, to facilitate the transfer of amino groups. Pyridoxal phosphate acts as a cofactor, binding to the enzyme and enabling the catalytic activity of aminotransferases. This relationship between the enzyme and the coenzyme is essential for the proper functioning of aminotransferases in the metabolism of amino acids and the regulation of nitrogen balance. The dependence of aminotransferases on pyridoxal phosphate highlights the importance of adequate vitamin B6 intake for maintaining healthy liver function and overall nitrogen metabolism.

Related terms

Deamination:

The process of removing an amino group from an amino acid, resulting in the formation of an alpha-keto acid.

Transamination:

The reversible transfer of an amino group from one molecule (typically an amino acid) to another, often an alpha-keto acid.

Coenzymes:

Small, non-protein molecules that assist enzymes in catalyzing specific chemical reactions, such as the transfer of amino groups.