Phenylalanine is an essential aromatic amino acid required for protein synthesis in humans. It serves as a precursor for tyrosine, dopamine, norepinephrine, and epinephrine. Naturally occurring in protein-rich foods such as meat, fish, eggs, dairy, and soy. The L-isomer is biologically active. It is used in aspartame production and as a dietary supplement. Phenylalanine exhibits low water solubility at room temperature and is stable under normal conditions but decomposes at high temperatures. In biochemistry, it participates in the shikimate pathway in plants and microorganisms.