Tyrosine was discovered in casein in the mid-19th century, and there are two isomers of tyrosine, l-tyrosine and D-tyrosine. Among them, L-tyrosine is widely used, not only as a configuration in organisms, but also plays an important role in the synthesis of melanin.
Melanin, a nitrogenous melanin produced by melanocytes, is distributed in tissues such as hair, skin and choroid of optic nerves. L-tyrosine is the precursor of melanin synthesis in the process of melanin synthesis. Under the catalysis of tyrosinase, L-tyrosine is hydroxylated into dopamine and then converted into dopamine quinone. At the beginning, dopamine quinone can react automatically to obtain indolequinone through the side chain, and the effect of melanin synthesis is achieved after polymerization.