Aspartate aminotransferase

We probably have rarely heard of aspartate aminotransferase in our daily lives, and we don’t know what it is used to measure. In fact, aspartate aminotransferase is a common manifestation of aminotransferase and is a very important indicator in liver function tests. Through the changes in this data, we can well judge what kind of diseases we have in our liver. Let us take a closer look at it below.

There will be an item called aspartate aminotransferase in liver function tests. Some people have found that their aspartate aminotransferase levels are high during the test. Many people don’t know what is going on or what disease causes it. Let’s take a look at the introduction related to aspartate aminotransferase.

L-Aspartate aminotransferase is a type of aminotransferase that catalyzes the transamination of aspartate and α-ketoglutarate to form glutamate and oxaloacetate. AST is widely distributed in various tissues of the human body, but the content in each tissue varies. AST is mainly distributed in the myocardium, followed by the liver, kidney and skeletal muscle. It is distributed in the cytoplasm and mitochondrial matrix, but about 80% of AST exists in mitochondria and is an intracellular functional enzyme. Zone electrophoresis confirmed that tissue cells contain positively charged (swimming toward the cathode) mitochondrial AST (m-AST) and negatively charged (swimming toward the anode) cytosolic AST (C-AST), both of which are dimers composed of two peptide chains. The molecular weight of m-AST is 9.1kD and that of C-AST is 9.3Kd, but their amino acid composition, optimal pH, substrate, immunological properties and the rate of excretion from the bloodstream are completely different. Since m-AST is located in the mitochondria and is not easily released into the blood, normal human serum mainly contains C-AST and the m-AST content is very low. The content in normal human serum is very low, but when liver cells or cardiomyocytes are damaged, due to increased cell membrane permeability, ALT and AST in the cytoplasm are released into the plasma, resulting in increased transaminase activity in the serum.

In liver function tests, alanine aminotransferase is an indicator of liver cell damage, while aspartate aminotransferase is a standard for liver cell necrosis. It is very accurate in detecting cirrhosis, liver fibrosis and liver cancer. It can be combined with alanine aminotransferase to reflect the status of liver function. For example, an alanine aminotransferase/aspartate aminotransferase ratio below 1.0 indicates patients with cirrhosis or early cirrhosis.

Many literatures report that the ratio of AST to ALT helps determine the severity of liver disease and has certain significance in diagnosis. ①When liver cells are damaged, AST/ALT <1. ② When the AST/ALT ratio is greater than 1, it is common in cirrhosis of various causes; in chronic viral hepatitis, it often indicates fibrosis or progression of cirrhosis; in the late stage of acute hepatitis, it indicates a tendency to severe hepatitis. If it is greater than 2, the prognosis is poor. ③ When the AST/ALT ratio is greater than 2 and the AST level is less than 300, it often indicates alcoholic liver disease; in addition to alcoholic damage, systemic diseases, myocardial damage, etc. may also cause AST/ALT to be greater than 1 or 2. ④ When the AST/ALT ratio is greater than 3 and AST is greater than 500, it indicates circulatory disorders such as left ventricular failure or liver malignancy.

In liver function tests, elevated aspartate aminotransferase levels are not necessarily caused by hepatitis. Because drinking, fatigue, staying up late, strenuous exercise, and medications may all cause elevated aspartate aminotransferase levels, you don't need to be too nervous if aspartate aminotransferase levels are elevated. You just need to go to a regular hospital for a confirmed diagnosis.

Transaminases are a class of enzymes that catalyze the transfer of amino groups between amino acids and keto acids. It is widely found in animal and plant tissues and microorganisms, and its content is higher in animal tissues such as the myocardium, brain, liver, and kidney, as well as in mung bean sprouts. There are many types. Except for lysine and threonine, the other α-amino acids in the body can participate in transamination and each has its own specific transaminase. Among them, alanine aminotransferase (GPT) and aspartate aminotransferase (GOT) are the most important.

Many people are not very familiar with the phenomenon of high aspartate aminotransferase. Through our introduction today, I believe everyone should be aware of this. This may be due to some reasons in our liver, but it is not necessarily caused by hepatitis. Some external factors, such as drinking, fatigue, strenuous exercise, and staying up late can cause this phenomenon.