nutrient
Phenylalanine
An essential aromatic amino acid that supplies tyrosine.
Phenylalanine is incorporated into proteins and can be converted to tyrosine, which then enters specialised pathways.
A precursor for tyrosine
Phenylalanine hydroxylase converts phenylalanine to tyrosine. Tyrosine can then enter catecholamine, thyroid-hormone and melanin pathways.
Related topics
Phenylalanine is used to build Protein
Phenylalanine is one of the amino acids used to assemble proteins.
Worth knowing
It is required from dietary protein. Humans cannot make enough phenylalanine and obtain it from dietary protein.
A closer look
The conversion is enzyme-controlled
The rate at which phenylalanine becomes tyrosine depends on enzyme activity and amino-acid handling.
The conversion has an enzyme step
Phenylalanine hydroxylase converts phenylalanine to tyrosine before tyrosine enters its own specialised pathways.
References
Source-checked local draft.
Human editorial review pending.
- NIH National Library of MedicineBiochemistry, Essential Amino AcidsChecked 2026-09-05
- NIH National Library of MedicineBiochemistry, Protein CatabolismChecked 2026-09-05