Phenylalanine
![Human biosynthesis pathway for trace amines and catecholamines[6][7]
L-Phenylalanine
L-Tyrosine
L-Dopa
Epinephrine
Phenethylamine
p-Tyramine
Dopamine
Norepinephrine
N-Methylphenethylamine
N-Methyltyramine
p-Octopamine
Synephrine
3-Methoxytyramine
AADC
AADC
AADC
PNMT
PNMT
PNMT
PNMT
AAAH
AAAH
COMT
DBH
DBH
Phenylalanine in humans may ultimately be metabolized into a range of different substances.](/uploads/202502/02/Catecholamine_and_trace_amine_biosynthesis3204.png)
Phenylalanine (US: /ˌfɛnəlˈæləniːn/, UK: /ˌfiːnaɪlˈæləniːn/; abbreviated as Phe or F) is an α-amino acid with the formula C6H5CH2CH(NH2)COOH. It can be viewed as a benzyl group substituted for the methyl group of alanine, or a phenyl group in place of a terminal hydrogen of alanine. This essential amino acid is classified as neutral, and nonpolar because of the inert and hydrophobic nature of the benzyl side chain. The L-isomer is used to biochemically form proteins, coded for by DNA. The codons for L-phenylalanine are UUU and UUC. Phenylalanine is a precursor for tyrosine; the monoamine neurotransmitters dopamine, norepinephrine (noradrenaline), and epinephrine (adrenaline); and the skin pigment melanin.