AST

Aspartate Aminotransferase (AST) is an enzyme that plays a vital role in amino acid metabolism. It is found in various tissues throughout the body, with high concentrations in the liver, heart, muscles, kidneys, and brain. AST catalyzes the transfer of an amino group from aspartate to alpha-ketoglutarate, producing glutamate and oxaloacetate. This reaction is crucial for the synthesis and breakdown of amino acids and for the production of glucose and urea.

Function

The primary function of AST is to facilitate the reversible transfer of an amino group between aspartate and alpha-ketoglutarate, which is a key step in the citric acid cycle and urea cycle. This process is essential for the metabolism of amino acids, which are the building blocks of proteins. In the liver, AST plays a significant role in gluconeogenesis, the process by which glucose is synthesized from non-carbohydrate sources.

Clinical Significance

Elevated levels of AST in the blood are an indicator of tissue damage, particularly in the liver, heart, and muscles. As such, AST is commonly measured in blood tests to assess liver health and to diagnose and monitor various conditions, including hepatitis, cirrhosis, and myocardial infarction. It is often measured alongside alanine aminotransferase (ALT), another liver enzyme, to evaluate liver function.

AST in Diagnosis

The AST to ALT ratio is a useful diagnostic tool. A ratio greater than 1 is typically indicative of liver damage due to conditions other than fatty liver disease, such as alcoholic liver disease or cirrhosis. Conversely, a ratio less than 1 is commonly seen in non-alcoholic fatty liver disease.

Measurement

AST levels are measured through a blood test. The normal range for AST levels can vary between laboratories, but it is generally between 10 to 40 units per liter. Elevated AST levels need to be interpreted in conjunction with other diagnostic tests and clinical findings.

Conclusion

Aspartate Aminotransferase is a crucial enzyme in amino acid metabolism, with significant roles in the liver, heart, and other tissues. Its measurement is an important diagnostic tool in assessing liver and muscle health. Understanding AST levels, in conjunction with other tests, can help diagnose and monitor various medical conditions.