Protein Metabolism

Glycolysis &
Citric Acid Cycle
Lipid Metabolism &
Review Metabolism
 Elmhurst College
Transamination Urea Cycle Energy Summary  Chemistry Department
Oxidative Deamination Bilirubin - Heme Catabolism  PKU  Virtual ChemBook



Oxidative Deamination Reaction

Introduction:

Deamination is also an oxidative reaction that occurs under aerobic conditions in all tissues but especially the liver. During oxidative deamination, an amino acid is converted into the corresponding keto acid by the removal of the amine functional group as ammonia and the amine functional group is replaced by the ketone group. The ammonia eventually goes into the urea cycle.

Oxidative deamination occurs primarily on glutamic acid because glutamic acid was the end product of many transamination reactions.

The glutamate dehydrogenase is allosterically controlled by ATP and ADP. ATP acts as an inhibitor whereas ADP is an activator.

 

Link to: Transamination and Deamination (move cursor over arrows)
Jim Hardy, Professor of Chemistry, The University of Akron.


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Central Role for Glutamic Acid:

Apparently most amino acids may be deaminated but this is a significant reaction only for glutamic acid. If this is true, then how are the other amino acids deaminated? The answer is that a combination of transamination and deamination of glutamic acid occurs which is a recycling type of reaction for glutamic acid. The original amino acid loses its amine group in the process. The general reaction sequence is shown on the left.


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Synthesis of New Amino Acids:

The same reaction works in reverse for the synthesis of amino acids. In this situation alpha-ketoglutaric acid first uses transamination of a different amino acid to make glutamic acid, which then reacts with a keto acid to make a new amino acid.

In effect, the interconversion of alpha-ketoglutaric acid and glutamic acid lies at the very heart of nitrogen metabolism. These molecules serve as the "collection and receiving agent" for nitrogen. The subsequent fate of the amino group is in new amino acids, any nitrogen bases, or any other nitrogen containing compounds.