Glutamine—pyruvate transaminase

Glutamine—pyruvate transaminase (GPT), also known as alanine transaminase (ALT), is an enzyme that plays a crucial role in amino acid metabolism and the urea cycle. This enzyme facilitates the conversion of glutamine and pyruvate into glutamate and alanine, respectively. This process is essential for the detoxification of ammonia in the liver, the synthesis of amino acids, and energy production. GPT is predominantly found in the liver, but it is also present in lesser amounts in the kidneys, heart, and muscles.

Function

The primary function of GPT is to catalyze the reversible transamination between glutamine and pyruvate to produce glutamate and alanine. This reaction is vital for the metabolism of amino acids, which are the building blocks of proteins. GPT plays a significant role in the glucose-alanine cycle, which helps in the transport of ammonia and pyruvate from muscles to the liver. In the liver, ammonia is converted into urea and excreted from the body, while pyruvate can be used in the gluconeogenesis pathway to produce glucose.

Clinical Significance

Elevated levels of GPT in the blood are an indicator of liver damage or liver disease, such as hepatitis or cirrhosis. Since GPT is highly concentrated in the liver, its presence in the blood usually signifies liver cell injury. Therefore, GPT is commonly measured in liver function tests to assess the health of the liver. It is also measured to monitor the treatment of patients with liver disease, to gauge the extent of liver damage, and to follow the progression of liver conditions.

Genetics

The gene encoding the GPT enzyme is located on the human chromosome. Mutations in this gene can affect the enzyme's function and lead to metabolic disorders. Research is ongoing to better understand the genetic variations that influence GPT activity and their implications for liver disease and other metabolic conditions.

See Also

• Liver function tests
• Amino acid metabolism
• Urea cycle
• Glucose-alanine cycle