Phenylalanine Metabolism: From Amino Acid To Tyrosine

Phenylalanine Metabolism: From Amino Acid To Tyrosine

Name the aromatic amino acids. Describe the metabolism of any one of them.
Answer:

Aromatic amino acids:

1. Phenylalanine
2. Tyrosine
3. Tryptophan.

Metabolism of phenylalanine:

1. Conversion of phenylalanine to tyrosine.
2. Phenylalanine is hydroxylated at the para position by phenylalanine hydroxylase to produce tyrosine.
3. It involves the incorporation of one atom of molecular oxygen into the para position of phenylalanine while the other atom of O2 is reduced to form water.
4. It is an irreversible reaction.
5. It requires specific coenzyme biopterin.
6. The active form of biopterin is tetrahydrobiopterin.
7. Tetrahydrobiopterin is oxidized to dihydrobiopterin.
8. Then tetrahydrobiopterin is regenerated by NADPH – dependent dihydropterin reductase.

1. Fumarate- uses:
   • Intermediate of the citric acid cycle.
   • Precursor for gluconeogenesis.
2. Acetoacetate – uses:
   • Source for fat synthesis.