aromatic amino acid family biosynthetic process

Definition

Target type: biologicalprocess

The chemical reactions and pathways resulting in the formation of aromatic amino acid family, amino acids with aromatic ring (phenylalanine, tyrosine, tryptophan). [GOC:go_curators]

The biosynthesis of aromatic amino acids, phenylalanine, tyrosine, and tryptophan, is a complex and essential metabolic pathway for all living organisms. This process is vital for protein synthesis, as these amino acids serve as building blocks for proteins and enzymes crucial for numerous biological functions. Here's a detailed description of the process:

**1. Shikimate Pathway:**

This pathway, common in plants, fungi, and bacteria, is the initial step in aromatic amino acid biosynthesis. It begins with the condensation of phosphoenolpyruvate (PEP), a product of glycolysis, with erythrose 4-phosphate, a product of the pentose phosphate pathway. This reaction is catalyzed by the enzyme DAHP synthase, and it forms 3-deoxy-D-arabino-heptulosonate 7-phosphate (DAHP).

The subsequent steps involve a series of enzymatic reactions that convert DAHP to chorismate, a key branch point metabolite. Chorismate is the precursor for all three aromatic amino acids:

* **Phenylalanine:** Chorismate is converted to prephenate by chorismate mutase. Prephenate is then decarboxylated and transaminated to form phenylalanine.
* **Tyrosine:** Chorismate is directly converted to tyrosine by a two-step reaction catalyzed by the enzyme chorismate mutase/prephenate dehydrogenase.
* **Tryptophan:** Chorismate is first converted to anthranilate by anthranilate synthase. Anthranilate then undergoes several steps involving condensation with phosphoribosyl pyrophosphate (PRPP) and glutamine to form tryptophan.

**2. Regulation:**

The biosynthesis of aromatic amino acids is tightly regulated at multiple points. Feedback inhibition, where the final products of the pathway inhibit the activity of key enzymes, is a common mechanism. For example, phenylalanine and tyrosine can inhibit DAHP synthase. This regulation ensures that the production of aromatic amino acids is balanced with cellular needs and prevents the accumulation of excess amounts.

**3. Importance:**

* **Protein Synthesis:** Aromatic amino acids are essential building blocks for proteins, including enzymes involved in diverse metabolic pathways.
* **Neurotransmitters:** Tyrosine is a precursor to dopamine, norepinephrine, and epinephrine, crucial neurotransmitters involved in mood regulation, alertness, and stress response.
* **Pigments:** Tyrosine is a precursor to melanin, the pigment responsible for skin and hair color.
* **Plant Hormones:** Tryptophan is a precursor to auxin, a plant hormone that regulates growth and development.

**4. Evolutionary Significance:**

The shikimate pathway is absent in animals, highlighting the importance of these amino acids in their diet. This pathway's presence in bacteria and plants makes it a target for herbicide development, as blocking this pathway would disrupt the growth of unwanted plants.

**In summary, the biosynthesis of aromatic amino acids is a complex and vital metabolic process with far-reaching implications for life. This pathway is essential for protein synthesis, the production of key neurotransmitters and pigments, and the regulation of plant growth and development.**
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Proteins (4)

Compounds (3)