Aminotransferases

Aminotransferases

Aminotransferases, also known as transaminases, are enzymes that play a crucial role in the metabolism of amino acids. They catalyze the transfer of an amino group from an amino acid to a keto acid, a process that is essential for the synthesis and degradation of amino acids. This article will explore the structure, function, and clinical significance of aminotransferases.

Structure and Function

Aminotransferases are a group of enzymes that belong to the class of transferases. They require the coenzyme pyridoxal phosphate (PLP), a derivative of vitamin B6, to function. PLP acts as a cofactor by forming a Schiff base with the amino group of the substrate, facilitating the transfer of the amino group.

The general reaction catalyzed by aminotransferases is:

α-amino acid + α-keto acid ⇌ α-keto acid + α-amino acid

The most common aminotransferases are:

• Alanine aminotransferase (ALT), also known as glutamate-pyruvate transaminase (GPT), which catalyzes the conversion of alanine and α-ketoglutarate to pyruvate and glutamate.
• Aspartate aminotransferase (AST), also known as glutamate-oxaloacetate transaminase (GOT), which catalyzes the conversion of aspartate and α-ketoglutarate to oxaloacetate and glutamate.

Clinical Significance

Aminotransferases are important biomarkers in clinical medicine, particularly in the assessment of liver function. Elevated levels of ALT and AST in the blood can indicate liver damage or disease, such as hepatitis, cirrhosis, or liver cancer.

Alanine Aminotransferase (ALT)

ALT is primarily found in the liver, and its levels are more specific to liver injury. Elevated ALT levels are often seen in conditions such as:

• Viral hepatitis
• Non-alcoholic fatty liver disease (NAFLD)
• Alcoholic liver disease

Aspartate Aminotransferase (AST)

AST is found in various tissues, including the liver, heart, and muscles. Therefore, elevated AST levels can indicate damage to these tissues. Conditions associated with elevated AST include:

• Myocardial infarction
• Muscle disorders
• Liver diseases

Diagnostic Use

The ratio of AST to ALT, known as the De Ritis ratio, can provide additional diagnostic information. A ratio greater than 2:1 is often associated with alcoholic liver disease, while a lower ratio may suggest non-alcoholic liver conditions.

Conclusion

Aminotransferases are vital enzymes in amino acid metabolism and serve as important clinical markers for liver and other tissue damage. Understanding their function and clinical implications is essential for diagnosing and managing various medical conditions.