Which among the following amino acid is heterocyclic in structure?
Histidine and tryptophan are heterocyclic amino acids. Phenylalanine and tyrosine are aromatic amino acids. Proline is an imino acid. Hydroxyproline, hydroxylysine, and ornithine are derived amino acids. Ref: Textbook of Biochemistry for Medical Students By Dm Vasudevan, 2010, Page 20.
Histidine
Phenylalanine
Hydroxyproline
Proline