Oxidative deamination is the liberation of free ammonia from the amino group of the amino acid coupled with oxidation. This takes place mostly in liver and kidney. The purpose of oxidative deamination is to provide NH3 for urea synthesis and α-keto acid for a variety of reactions, including energy generation.
The removal of amino group from the amino acid as NH3 is termed as deamination. Transamination involves only the shuffling of amino groups among the amino acids. On the other hand, deamination results in the liberation of ammonia for urea synthesis. These reactions occur primarily in liver and kidney and provide α-keto acid (which can enter the central…
Formation of enzyme pyridoxal phosphate-Schiff base and amino add-pyridoxal phosphate Schiff base.
Involvement of pyridoxal phosphate in the transfer of amino group.
All amino transferase requires the coenzyme pyridoxal phosphate (a derivative of vitamin B6), which is covalently linked to an e-amino group of a specific lysine residue at the active site of the enzyme (Schiff base) as shown in Figure 9.4. Amino transferase transfers the amino group from an amino acid to the pyridoxal part of the…
Serum glutamate oxaloacetate transferase, also known as aspartate transaminase (AST), is the exception to the rule that amino transferase funnels amino groups to form glutamate. AST transfers amino groups from glutamate to oxaloacetate, thus forming aspartate, which acts as a source of nitrogen in the urea cycle.
Serum glutamate pyruvate transferase is present mostly in liver. This enzyme catalyses the transfer of the amino group from alanine to α-ketoglutarate, resulting in the formation of pyruvate and glutamate. This reaction is reversible, so during amino acid metabolism the enzyme proceeds towards the direction of glutamate synthesis. Thus, glutamate is considered to be the collector…
Each amino transferase is specific for one or at most a few amino group donors. Amino transferases are named after the specific amino group donors because the acceptor of the amino acid is almost always α-ketoglutarate. The most important amino transferase reactions are catalysed by alanine amino transferase or serum glutamate pyruvate transaminase (SGPT) and…
Figure 9.3 Transamination Reaction
Transamination is defined as the transfer of amino group (—NH2) from an amino acid to keto acid. This process entails the inter-conversion of a pair of amino acids and a pair of keto acids catalysed by a group of enzymes known as transaminases (amino transferases) as shown in Figure 9.3.