The deamination of amino acids


Many amino acids (1) drop their amine group to coenzyme pyridoxylphosphate (6) while transforming into the corresponding ketoacids (2) . The pyridoxamine (5) formed, in turn, frequently transforms the α-ketoglutaric acid (3) (see →     Krebs cycle ) in glutamic acid (4) . Glutamic acid is an important amino acid that is used as a neurotransmitter or reused in protein biosynthesis, or to remove excess nitrogen in ureogenesis.


Alanine + $ \alpha$ -cetoglutarate $ \rightarrow $pyruvate (see →     glycolysis ) + glutamic acid Equation: ..........

Aspartic acid + $ \alpha $-ketoglutarate $ \rightarrow $oxaloacetate + glutamic acid Equation: ..........

Oxidative deamination

Dehydrogenases using as coenzyme the nicotinamidedinucleotide $NAD^+ $ trnasform certain amino acids into corresponding ketoacids for example:

Thus the glutamic acid (4) formed by transamination can be converted back into & alpha;-ketoglutaric acid (3) ( AA deamination cycle!)