Transamination transfers amino groups between molecules, allowing for the synthesis and degradation of amino acids without producing toxic ammonia. The process also facilitates the synthesis of non-essential amino acids and can convert alpha-keto acids into energy sources. Aminotransferases catalyze the reaction, requiring pyridoxal phosphate as a cofactor. ALT and AST are common human transaminases, and their levels in the blood can indicate liver damage.
Transamination, taken literally, means the transfer of an amino group from one molecule to another. In many organisms, this process is used to both synthesize and degrade amino acids. One major cellular advantage of the reaction is that it allows for the transfer of an amino group without the formation of ammonia, which is a toxic byproduct. In humans, it occurs mainly in the liver and is also known as an aminotransfer.
From a biochemical point of view, this is a redox reaction that transfers the amino group from an amino acid to an alpha-keto acid. This results in the creation of a new amino acid and a new alpha-keto acid. With this definition, interconversion may actually be a better term to describe the exchange of amino groups. The alpha-keto acids formed can be converted into lipids, glucose or glycogen. In this way, proteins obtained from food consumption can be used for the current or future energy needs of cells.
Transamination is also critical in humans for anabolic functions, such as the synthesis of non-essential amino acids. Humans need around 20 amino acids to build proteins, which are needed to synthesize hormones and enzymes and are involved in many physiological functions. Eight amino acids are called essential and must be obtained from dietary intake. The remaining amino acids are termed non-essential because the body can use other substances to synthesize them.
Among the non-essential amino acids, alanine, aspartate and glutamate are among the most common. Glutamate is synthesized from alpha-ketoglutarate. This alpha keto acid is created during the metabolism of dietary proteins. Glutamate can then undergo transamination to form alanine and aspartate. All other non-essential amino acids are made up of these three.
Aminotransfer is facilitated by enzymes called aminotransferases or transaminases. These enzymes have broad activity, which means they can catalyze reactions with different types of amino acids. For the activity, a cofactor is required which acts as an intermediate transporter of the amino group during the reaction. For transaminases, the required cofactor is pyridoxal phosphate, which is the active form of vitamin B6.
Alanine aminotransferase (ALT) and aspartate aminotransferase (AST) are the two most common human transaminases. These two enzymes are found in many tissues in the body, including the liver and heart. If those tissues are damaged due to disease, the damaged cells release enzymes into the bloodstream. Healthcare professionals often measure ALT and AST in the blood to diagnose and monitor liver damage.
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