- Function: Converts tryptophan to 5-hydroxytryptophan (5-HTP), a precursor to serotonin.
- Tissue Specificity: Expressed mainly in peripheral tissues (gut, pineal gland).
- Biological Importance:
- Controls peripheral serotonin levels.
- Implicated in mood, behavior, and gastrointestinal function.
- Clinical Relevance:
- Mutations linked to serotonin-related disorders.
- Potential target for mood and sleep disorder treatments.
- Function: Converts phenylalanine to tyrosine, a key metabolic step.
- Tissue Specificity: Primarily in liver tissue.
- Biological Importance:
- Maintains normal phenylalanine levels.
- Supplies tyrosine for neurotransmitter synthesis.
- Clinical Relevance:
- Mutations cause Phenylketonuria (PKU).
- PKU leads to neurotoxicity if untreated.
| Feature | TPH1 | PAH |
|---|---|---|
| Enzymatic Role | Serotonin biosynthesis | Amino acid metabolism |
| Primary Substrate | Tryptophan | Phenylalanine |
| Product | 5-Hydroxytryptophan | Tyrosine |
| Main Tissue | Gut, pineal gland | Liver |
| Clinical Relevance | Mood & gut disorders | Phenylketonuria (PKU) |