Question

(a) What products are formed when each peptide is treated with trypsin? (b) What products are formed when each peptide is treated with chymotrypsin?

[1] Gly–Ala–Phe–Leu–Lys–Ala

[2] Phe–Tyr–Gly–Cys–Arg–Ser

[3] Thr–Pro–Lys–Glu–His–Gly–Phe–Cys–Trp–Val–Val–Phe

Short answer

Cleavage by Trypsin:

[1] Gly–Ala–Phe–Leu–Lys + Ala

[2] Phe–Tyr–Gly–Cys–Arg + Ser

[3] Thr–Pro–Lys + Glu–His–Gly–Phe–Cys–Trp–Val–Val–Phe

Cleavage by Chymotrypsin

[1] Gly–Ala–Phe + Leu–Lys–Ala

[2] Phe + Tyr + Gly–Cys–Arg–Ser

[3] Thr–Pro–Lys–Glu–His–Gly–Phe + Cys–Trp + Val–Val–Phe

Step-by-step solution

Hydrolysis of peptides by enzymes

The peptide bonds can be hydrolyzed at specific sites by the enzymes like trypsin, chymotrypsin, and carboxypeptidase.

Cleavage by Trypsin

Trypsin catalyzes the hydrolysis of amides with a carbonyl group that is part of the basic amino acids arginine and lysine.

[1] Gly–Ala–Phe–Leu–Lys + Ala

[2] Phe–Tyr–Gly–Cys–Arg + Ser

[3] Thr–Pro–Lys + Glu–His–Gly–Phe–Cys–Trp–Val–Val–Phe

Cleavage by Chymotrypsin

Chymotrypsin hydrolyzes amides with carbonyl group that is part of the aromatic amino acids phenylalanine, tyrosine, and tryptophan.

[1] Gly–Ala–Phe + Leu–Lys–Ala

[2] Phe + Tyr + Gly–Cys–Arg–Ser

[3] Thr–Pro–Lys–Glu–His–Gly–Phe + Cys–Trp + Val–Val–Phe