Phenylalanine
L-phenylalanine (LPA) serves as a building block for the various proteins that are produced in the body. LPA can be converted to L-tyrosine (another amino acid) and subsequently to L-dopa, norepinephrine, and epinephrine. LPA can also be converted (through a separate pathway) to phenylethylamine, a substance that occurs naturally in the brain and appears to elevate mood.