tryptophan biosynthetic process

Definition

Target type: biologicalprocess

The chemical reactions and pathways resulting in the formation of tryptophan, the chiral amino acid 2-amino-3-(1H-indol-3-yl)propanoic acid; tryptophan is synthesized from chorismate via anthranilate. [GOC:mah, ISBN:0471331309, MetaCyc:TRPSYN-PWY]

The tryptophan biosynthetic process is a complex metabolic pathway that involves multiple enzymatic steps to synthesize the essential amino acid tryptophan from the precursor molecule chorismate. This process is crucial for all living organisms as tryptophan is a building block for proteins, a precursor for various neurotransmitters including serotonin and melatonin, and plays a role in gene regulation. The biosynthesis of tryptophan can be broadly divided into two phases:

**Phase 1: Chorismate to Anthranilate**

* **Chorismate mutase** catalyzes the conversion of chorismate to prephenate, a key intermediate in the biosynthesis of aromatic amino acids.
* **Prephenate dehydratase** converts prephenate to phenylpyruvate, a precursor for phenylalanine synthesis.
* **Anthranilate synthase** is a multi-enzyme complex that catalyzes two reactions:
* Conversion of chorismate to N-(5'-phosphoribosyl)-anthranilate.
* Hydrolysis of the phosphoribosyl group to yield anthranilate.

**Phase 2: Anthranilate to Tryptophan**

* **Anthranilate phosphoribosyltransferase** catalyzes the reaction of anthranilate with 5-phospho-α-D-ribose 1-diphosphate (PRPP) to form N-(5'-phosphoribosyl)anthranilate.
* **Phosphoribosyl anthranilate isomerase** rearranges the molecule to form 1-(o-carboxyphenylamino)-1-deoxyribulose 5-phosphate (CdRP).
* **Indole-3-glycerol phosphate synthase** catalyzes a complex reaction involving decarboxylation and cyclization of CdRP to form indole-3-glycerol phosphate.
* **Tryptophan synthase** is a two-subunit enzyme that catalyzes the final step of the pathway:
* The α subunit cleaves indole-3-glycerol phosphate to form indole and D-glyceraldehyde 3-phosphate.
* The β subunit combines indole with serine to produce tryptophan.

The entire tryptophan biosynthesis pathway is tightly regulated to ensure that tryptophan levels are maintained within a specific range, preventing the accumulation of toxic intermediates and optimizing cellular function. Regulation occurs at multiple levels, including feedback inhibition of key enzymes by tryptophan, transcriptional control of gene expression, and post-translational modifications of enzymes.'
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Proteins (4)

Compounds (1)