| PubChem = 1153 | SMILES = N[C@@H](Cc1ccc(O)cc1)C(O)=O }} | Section2 = | Section3 = }} Tyrosine (abbreviated as Tyr or Y) or 4-hydroxyphenylalanine,'s one of the 20 amino acids that're used by cells to synthesize proteins. This's a non-essential amino acid and it's found in casein. Tyrosine has a polar side group. The word "tyrosine"'s from the Greek tyros, meaning cheese, as it was first discovered in 1846 by German chemist Justus von Liebig in the protein casein from cheese. Functions Aside… (More on Tyrosine)