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Aspartate aminotransferase is a type of enzyme that is generally localized to the liver and heart, whose activity is measured in a lab test to check for damage to these organs. It is also commonly known as aspartate transaminase. The aspartate aminotransferase (AST) test can be used specifically to check for liver or heart problems, or it can be part of standard medical test screening.
The liver has a number of aminotransferases, but the ones used in medical tests are alanine aminotransferase and aspartate aminotransferase. AST is found in more places in the body, and can be used as an indicator of a greater number of problems. Alanine aminotransferase is generally found only in the liver.
In addition to being found in the liver, aspartate aminotransferase is also found in skeletal and heart tissue. In healthy tissue, AST is found within cells and is only present at low levels in blood serum. If the tissue is damaged, however, this enzyme leaks into the blood serum and is found at elevated levels.
The AST test was previously used in cardiology to diagnose heart attacks, but has since been supplanted by other tests. Muscle disorders are another area in which AST levels can be elevated. This includes Duchenne’s muscular dystrophy and a condition known as myositis.
The primary use of the AST test, however, is to test for liver damage and monitor the treatment of liver disorders. It is a highly reliable marker for liver abnormalities. Low elevations in AST levels are hard to interpret, since they could indicate a serious disorder or be benign. For instance, if a person has an alcoholic drink a few hours before having his blood drawn, that beverage can cause an increase in AST levels.
Lower levels of AST elevation can be due to alcohol consumption combined with acetaminophen, such as Tylenol®. Common medicines such as statins, aspirin, antibiotics, and narcotics can also cause slightly high levels. Very high levels are generally an indication of severe damage to the liver, such as hepatitis or necrosis. Another reason for high levels can be shock. Moderately high levels can be due to long-term liver diseases, such as cirrhosis or the abuse of alcohol.
Since so many factors can cause slight increases in AST levels, an increased level will usually merit further diagnostic work. This test is also used to analyze whether liver disease is being successfully treated. If the levels are decreasing, it may indicate that the liver is recovering. The sgot test is an older name for this analysis, referring to the older name of serum gluatamate-oxaloacetate transaminase (sgot) for AST.
Aspartate aminotransferase is one of a number of different enzymes that transfers an amino acid to another compound. Amino acids are the components of proteins. They contain an NH2—amino group on them. This type of reaction is important for the cell’s protein metabolism.