Source : Webster's Revised Unabridged Dictionary (1913)

present in small amount in the pancreas and spleen, and formed
in large quantity from the decomposition of proteid matter by
various means, -- as by pancreatic digestion, by putrefaction as
of cheese, by the action of boiling acids, etc. Chemically, it
consists of oxyphenol and amidopropionic acid, and by
decomposition yields oxybenzoic acid, or some other benzol
derivative. [Written also {tyrosine}.]

Source : WordNet®

tyrosine
     n : an amino acid found in most proteins; a precursor of several
         hormones