Aminotransferase

Aminotransferase (also known as transaminase) is an important class of enzymes that catalyze the transfer of an amino group from an amino acid to a keto acid. This process is a key step in the metabolism of amino acids and is essential for the synthesis and degradation of amino acids in the body.

Function

Aminotransferases play a crucial role in the catabolism and anabolism of amino acids. They facilitate the conversion of amino acids into α-keto acids and vice versa, which is vital for the citric acid cycle and the urea cycle. The most common aminotransferases are alanine aminotransferase (ALT) and aspartate aminotransferase (AST).

Types

There are several types of aminotransferases, each specific to different amino acids. The most studied aminotransferases include:

• Alanine aminotransferase (ALT): Primarily found in the liver, ALT is used as a marker for liver health.
• Aspartate aminotransferase (AST): Found in the liver, heart, and muscles, AST is used to diagnose liver and heart diseases.
• Glutamate aminotransferase: Involved in the metabolism of glutamate.

Mechanism

Aminotransferases operate through a two-step mechanism involving the formation of a Schiff base intermediate. The enzyme binds to the amino acid, facilitating the transfer of the amino group to the keto acid, forming a new amino acid and a new keto acid.

Clinical Significance

Elevated levels of aminotransferases in the blood can indicate liver damage, myocardial infarction, or muscle injury. ALT and AST are commonly measured in blood tests to assess liver function and diagnose liver diseases such as hepatitis and cirrhosis.

Related Enzymes

Aminotransferases are part of a larger group of enzymes known as transferases, which transfer functional groups from one molecule to another. Other related enzymes include kinases and phosphatases.

See Also

• Enzyme
• Metabolism
• Liver function tests
• Citric acid cycle
• Urea cycle