Around 20 amino acids are important for the synthesis of protein in the plant. The transamination reaction along with other like acids, alanine, glutamic acid and aspartic acid with amino transferase enzyme transfer the amino group.
α-ketoglutamic acid + NH3 + NADPH Glutamic acid + NAD The amino acid can be differentiated into five different groups:
1. The Glutamate family-α-ketoglutarate is the precursor for this family. Glutamate,
glutamine, arginine, and proline are the main amino acids belonging to this family.
2. Aspartate family- Oxaloacetate is the starting material for this group. The main examples of amino acid of this group are aspargine, isoleucine, threonine, aspartate and methionine.
3. Another example is Alanine-valine and leucine group.
4. The amino acid of serine glycine group.
5. Aromatic amino acids with pyruvate 3-phosphoglycerate phosphoenol pyruvate and erythrose 4-phosphate as starting material.
The amino acids synthesized from the intermediate of pentose phosphate pathways, glycolysis and citric acid cycle. Around ten of the amino acids synthesized through few of the enzymatic steps with precursor but rest (like aromatic amino acids) are complex in synthesis.
Around all 20 amino acids can synthesize the bacteria and plants but only half by the mammals.
Formation of Ornithine, Proline, Hydroxyproline and Arginine:
Aspartate and alanine made from oxaloacetate and pyruvate respectively through transamination of glutamate. Amidation of aspartate aspargine is formed and NH4 donated
by glutamine. Threonine, isoleucine, methionine, lysine, leucine and valine are among the essential amino acids. The biosynthesis of these amino acids is very complex and interconnected. Threonine, methionine and lysine are generated by aspartate. Valine, isoleucine, leucine and alanine are generated by pyruvate. Valine and isoleucine involve enzyme for their biosynthesis. In the formation of valine an intermediate is formed known as ketoisovalerate which is another important precursor for the synthesis of leucine. Formation of Tyrosine, Tryptophan and Phenylalanine
Erythrose 4 phosphate
Cohorismate is a major compound for the formation of phenylalanine, tryptophan and tyrosine.
Amino acid Biosynthetic families group by Metabolic Precursor:
• α-ketoglutarate – Glutamate, Glutamine, Proline, Arginine
• 3-phosphoglycerate- Serine, Glycine, Cystine
• Oxaloacetate- Aspartate, Aspargine, Methionine, Threonine, Lysine
• Pyruvate- Alanine, Valine, Leucine, Isoleucine
• Ribose-5-phosphate- Histidine
• Phosphoenol pyruvate and erythrose 4-phosphate-Tryptophan, Phenylalanine,