An aromatic polar amino acid with the formula HOC6
)COOH. The biosynthesis of tyrosine is similar to that of *phenylalanine
, diverging only in the last few reaction steps. Breakdown to acetyl CoA and fumaric acid occurs via phenylalanine. Like phenylalanine, tyrosine is a precursor of the isoquinoline alkaloids. It is also a precursor of various phenolic inhibitors, e.g. coumaric acid.