Amino acid of phenylalanine and tyrosine

Phenylalanine is an essential amino acid that serves as a precursor in the biosynthesis of other amino acids including tyrosine.

Phenylalanine and tyrosine together lead to the formation of thyroxin and epinephrine. In addition, tyrosine is the precursor from which the formation of melanin, pigment of skin, hair and part of the eye is made.

Thus, most phenylalanine is converted to tyrosine. Excess phenylalanine is normally eliminated from the body by hydroxylation to tyrosine.

Phenylalanine and tyrosine are used by the body to make the hormones adrenaline and thyroxine and are also involved in the formation of melanin, a pigment present in the skin, hair and part of the eye.

In phenylketonuria (PKU), the missing or defective protein is a liver enzyme that converts the essential amino acid phenylalanine to the amino acid tyrosine.

Without this enzyme, phenylalanine and its metabolites accumulate and damage the developing nervous system.

Phenylalanine and tyrosine share a common pathway of degradation, which occurs in liver, and ultimately yields fumarate and acetyl CoA.
Amino acid of phenylalanine and tyrosine