Tyrosine is metabolically synthesized from phenylalanine to become the para-hydroxy derivative of that important amino acid. This hydroxylated amino acid participates in the synthesis of many important biochemicals including the thyroid hormones, the melanin biological pigments, and the catecholamines, an important class of biological regulators. Tyrosine is incorporated into proteins and enzymes at the molar rate of 3.5 percent with respect to the other amino acids.