Phenylalanine

Phenylalanine (symbol Phe or F) is an essential α-amino acid. 
This essential amino acid is neutral and nonpolar. This is 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. 
Phenylalanine is a precursor for tyrosine, the monoamine neurotransmitters dopamine, norepinephrine (noradrenaline), epinephrine (adrenaline), and the skin pigment melanin. It is encoded by the codons UUU and UUC.