Transamination – Function and Role in Metabolism
Transamination is a biochemical reaction in which amino groups are transferred between amino acids and keto acids. It plays a central role in amino acid metabolism.
Things worth knowing about "Transamination"
Transamination is a biochemical reaction in which amino groups are transferred between amino acids and keto acids. It plays a central role in amino acid metabolism.
What is Transamination?
Transamination (also called aminotransfer reaction) is a fundamental biochemical process in human metabolism. During this reaction, an amino group (-NH2) is transferred from one amino acid to an alpha-keto acid (also known as an oxo acid). The result is a new amino acid, while the original amino acid is converted into a keto acid. The reaction is reversible and occurs without any net loss of nitrogen.
Mechanism of Action
Transamination is catalyzed by enzymes called transaminases or aminotransferases. These enzymes require pyridoxal phosphate (PLP), the active form of vitamin B6, as a coenzyme. The reaction proceeds in two steps:
- Step 1: The amino group from the donor amino acid is transferred to PLP, forming pyridoxamine phosphate (PMP) and a keto acid.
- Step 2: The amino group is then transferred from PMP to an acceptor keto acid, generating a new amino acid and regenerating PLP.
The most common acceptor in transamination is alpha-ketoglutarate (2-oxoglutarate), which is converted to glutamate. Glutamate thereby serves as a central collector of amino groups in metabolism.
Key Transaminases
Two clinically significant transaminases are:
- Aspartate Aminotransferase (AST, also known as GOT): Catalyzes the transfer of the amino group from aspartate to alpha-ketoglutarate. It is found primarily in the liver, heart muscle, and skeletal muscle.
- Alanine Aminotransferase (ALT, also known as GPT): Catalyzes the transfer of the amino group from alanine to alpha-ketoglutarate. It is predominantly active in the liver and is considered a specific marker for liver cell damage.
Biological Significance
Transamination serves several important functions in the human body:
- Amino acid synthesis: The body can produce non-essential amino acids by transferring amino groups to suitable keto acids.
- Amino acid degradation: Excess amino acids can be broken down by transferring their amino groups to alpha-ketoglutarate, which are then excreted via the urea cycle.
- Energy production: The keto acids produced during transamination can enter the citric acid cycle and be used for energy generation.
- Gluconeogenesis: Keto acids such as pyruvate or oxaloacetate derived from transamination can be used to synthesize new glucose molecules.
Clinical Relevance
In clinical practice, transaminases are important laboratory markers. Elevated levels of ALT and AST in the blood can indicate damage to the liver or other organs. Common causes of elevated transaminase levels include:
- Liver diseases such as hepatitis (liver inflammation), liver cirrhosis, or fatty liver disease
- Myocardial infarction (elevated AST)
- Medication use or alcohol consumption
- Intense physical exercise (elevated AST due to muscle breakdown)
Measuring these enzyme levels is therefore a standard component in the diagnosis of liver and heart conditions.
References
- Berg, J.M., Tymoczko, J.L., Stryer, L. (2018). Biochemistry. 8th edition. W.H. Freeman and Company, New York.
- Devlin, T.M. (2011). Textbook of Biochemistry with Clinical Correlations. 7th edition. Wiley-Liss, New York.
- World Health Organization (WHO). Laboratory reference ranges for liver function tests. Available at: https://www.who.int
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