Question

What are the products from the treatment of the following peptide with trypsin? Leu-Val-Ala-Arg-Phe-Val-Ala-Leu-Lys-Gly-Arg-Pro-Asp

a) 2 tetrapeptides and 1 hexapeptide
b) 2 dipeptides, 1 tetrapeptide and 1 pentapeptide
c) 2 tripeptides, 1 tetrapeptide and 3 free amino acids
d) 1 dipeptide, 1 tripeptide and 2 tetrapeptides

Answer 1

Upon treatment with trypsin, the peptide Leu-Val-Ala-Arg-Phe-Val-Ala-Leu-Lys-Gly-Arg-Pro-Asp will yield two tetrapeptides, one dipeptide, and one tripeptide, corresponding to option d) 1 dipeptide, 1 tripeptide and 2 tetrapeptides.

Step-by-step explanation:

Trypsin is a proteolytic enzyme that specifically cleaves peptide bonds at the carboxyl side of the amino acids lysine and arginine. Given the peptide sequence Leu-Val-Ala-Arg-Phe-Val-Ala-Leu-Lys-Gly-Arg-Pro-Asp and the specificity of trypsin, we can anticipate where the cleavages will occur.

Cleavage occurs:

• After Arg to yield Leu-Val-Ala-Arg
• After Lys to yield Phe-Val-Ala-Leu-Lys
• After the second Arg to yield Gly-Arg
• No cleavage after Pro because Pro is not a trypsin cleavage site

Therefore, treatment of this peptide by trypsin will result in the formation of two tetrapeptides (Leu-Val-Ala-Arg and Phe-Val-Ala-Leu), one dipeptide (Gly-Arg), and the remaining tripeptide being Pro-Asp since it does not contain internal lysine or arginine residues for trypsin to act on.

Thus, the correct products resulting from the treatment of the peptide with trypsin are: two tetrapeptides, one dipeptide, and one tripeptide. This corresponds to option d) 1 dipeptide, 1 tripeptide and 2 tetrapeptides.