1.1.5.3.2.3.3.C. Participation of Pyridoxal Phosphate in the Mechanism of Transamination

Pyridoxal Phosphate acts as intermediary in the reaction:

a)   First, it takes the amino group of the original amino acid (amino acid 1), and gives the oxygen to the carbon skeleton of the amino acid, yielding a a-ketoacid (a-ketoacid 1). Pyridoxal Phosphate becomes Pyridoxamine Phosphate in the process.
b)   In the second part of the reaction, the Pyridoxamine Phosphate gives the amino group to a ketoacid (ketoacid 2), yielding a new amino acid (amino acid 2) while the pirydoxal phosphate is regenerated.

1.1.5.3.2.3.3.D. Important couples in Transamination reactions:

• When the amino acid transaminated is Alanine it yields the ketoacid Pyruvate (and vice-versa)
• When the amino acid transaminated is Aspartate, the reaction yields the ketoacid Oxalacetate (and vice-versa)
• When the amino acid transaminated is Glutamate, the reaction yields the ketoacid a-ketoglutarate

1.1.5.3.2.3.3.E. Importance of Transamination

• Funneling the a-amino group of amino acids to a-keto glutarate to get glutamate (glutamate plays a central role in Nitrogen metabolism).
• Synthesis of non essential amino acids
• Interconnection between amino acid metabolism and Krebs Cycle.

The following reaction is a very good example of these three former observations:

1.1.5.3.2.3.3.F. Clinical Importance of Transaminases (Aminotransferases) study:

• Since amino transferases are intracellular enzymes, abundant in hepatic and cardiac tissues, serum aminotransferases such as serum glutamate-oxaloacetate-aminotransferase (SGOT) (also called aspartate aminotransferase, AST) and serum glutamate-pyruvate aminotransferase (SGPT) (also called alanine transaminase, ALT) classically have been used as clinical markers of these tissue damages, with increasing serum levels indicating an increased extent of damage.  

Figure 1.11: Nature’s strategy to synthesize amino acids by using pyridoxamine phosphate coenzyme to perform a transamination with a keto acid.