BIOMOLECULES AND ENZYMES

Detailed explanation-1: -L-Tryptophan is the unique protein amino acid (AA) bearing an indole ring: its biotransformation in living organisms contributes either to keeping this chemical group in cells and tissues or to breaking it, by generating in both cases a variety of bioactive molecules.

Detailed explanation-2: -Tryptophan (Trp, W) is one of three aromatic amino acids that minimally contain a six-membered benzene ring in their side chains, the other two being phenylalanine (Phe, F) and tyrosine (Tyr, Y).

Detailed explanation-3: -Nitrogen heterocycles in proteins Three nitrogen heterocycles are found in the 20 proteinogenic amino acids: proline, histidine, and tryptophan, the latter two containing heteroaromatic imidazole and indole rings respectively (figure 1c).

Detailed explanation-4: -Tryptophan is an essential amino acid with an indole nucleus. Humans cannot produce this amino acid themselves, but must obtain it through their diet.

Detailed explanation-5: -Whereas phenylalanine contains a phenyl group, tyrosine contains a 4-hydroxy phenyl group (making it both an AAA and a hydroxy AA), while tryptophan is aromatic due to its heterocyclic indole ring (Figure 1).