Table of contents

1. A Review of General Chemistry5h 5m
2. Molecular Representations1h 14m
3. Acids and Bases2h 46m
4. Alkanes and Cycloalkanes4h 17m
5. Chirality3h 39m
6. Thermodynamics and Kinetics1h 22m
7. Substitution Reactions1h 48m
8. Elimination Reactions2h 30m
9. Alkenes and Alkynes2h 9m
10. Addition Reactions3h 19m
11. Radical Reactions1h 58m
12. Alcohols, Ethers, Epoxides and Thiols2h 42m
13. Alcohols and Carbonyl Compounds2h 17m
14. Synthetic Techniques1h 26m
15. Analytical Techniques:IR, NMR, Mass Spect7h 3m
16. Conjugated Systems6h 13m
17. Ultraviolet Spectroscopy51m
18. Aromaticity2h 34m
19. Reactions of Aromatics: EAS and Beyond5h 1m
20. Phenols55m
21. Aldehydes and Ketones: Nucleophilic Addition4h 56m
22. Carboxylic Acid Derivatives: NAS2h 51m
23. The Chemistry of Thioesters, Phophate Ester and Phosphate Anhydrides1h 10m
24. Enolate Chemistry: Reactions at the Alpha-Carbon1h 53m
25. Condensation Chemistry2h 9m
26. Amines1h 43m
27. Heterocycles2h 0m
28. Carbohydrates5h 53m
29. Amino Acids4h 20m
30. Peptides and Proteins2h 42m
31. Catalysis in Organic Reactions1h 30m
32. Lipids 2h 50m
33. The Organic Chemistry of Metabolic Pathways2h 52m
34. Nucleic Acids1h 32m
35. Transition Metals6h 14m
36. Synthetic Polymers1h 49m

29. Amino Acids

Proteins and Amino Acids

Organic Chemistry

29. Amino Acids

Proteins and Amino Acids

Previous problemNext problem

5:54 minutes

Problem 50

Textbook Question

Show the peptides that would result from cleavage by the indicated reagent:
a. Val-Arg-Gly-Met-Arg-Ala-Ser by carboxypeptidase A
b. Ser-Phe-Lys-Met-Pro-Ser-Ala-Asp by cyanogen bromide
c. Arg-Ser-Pro-Lys-Lys-Ser-Glu-Gly by trypsin

Verified step by step guidance

Step 1: Understand the cleavage specificity of each reagent. Carboxypeptidase A cleaves amino acids from the C-terminal end, except for Pro, Arg, and Lys. Cyanogen bromide cleaves at the C-terminal side of methionine residues. Trypsin cleaves at the C-terminal side of arginine (Arg) and lysine (Lys) residues, unless followed by proline (Pro).

Step 2: For part (a), Val-Arg-Gly-Met-Arg-Ala-Ser by carboxypeptidase A, sequentially remove amino acids from the C-terminal end, stopping when encountering Arg (since carboxypeptidase A does not cleave after Arg). Write down the resulting peptides after each cleavage step.

Step 3: For part (b), Ser-Phe-Lys-Met-Pro-Ser-Ala-Asp by cyanogen bromide, locate the methionine (Met) residue in the sequence. Cleave at the C-terminal side of Met, resulting in two peptides. Write down the resulting peptide fragments.

Step 4: For part (c), Arg-Ser-Pro-Lys-Lys-Ser-Glu-Gly by trypsin, locate the arginine (Arg) and lysine (Lys) residues in the sequence. Cleave at the C-terminal side of these residues, unless followed by proline (Pro). Write down the resulting peptide fragments.

Step 5: Verify the cleavage products for each part by ensuring the rules of the specific reagent are followed and that the sequence is correctly divided into peptides. Double-check for any exceptions or special cases (e.g., Pro inhibiting cleavage by trypsin).

Verified video answer for a similar problem:

This video solution was recommended by our tutors as helpful for the problem above

Video duration:

Play a video:

Was this helpful?

Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Peptide Cleavage

Peptide cleavage refers to the process of breaking peptide bonds between amino acids in a protein or peptide chain. This can be achieved through various enzymes or reagents, each with specific cleavage sites. Understanding the mechanism of cleavage is essential for predicting the resulting peptide fragments.

Carboxypeptidase A

Carboxypeptidase A is an enzyme that catalyzes the hydrolysis of peptide bonds at the carboxy-terminal end of proteins and peptides. It preferentially cleaves off aromatic and aliphatic amino acids, which is crucial for determining the specific fragments produced from a peptide sequence when this enzyme is applied.

Cyanogen Bromide and Trypsin

Cyanogen bromide is a chemical reagent that cleaves peptide bonds specifically at the carboxyl side of methionine residues, while trypsin is a proteolytic enzyme that cleaves at the carboxyl side of lysine and arginine residues. Knowledge of these specificities is vital for predicting the products of peptide cleavage in biochemical analysis.

Watch next

Master Peptides and Polypeptides with a bite sized video explanation from Johnny

Start learning

Related Videos

Related Practice

Textbook Question

Show how you would use bromination followed by amination to synthesize the following amino acids.

(b) leucine

Textbook Question

The herbicide glyphosate (Roundup®) kills plants by inhibiting an enzyme needed for synthesis of phenylalanine. Deprived of phenylalanine, the plant cannot make the proteins it needs, and it gradually weakens and dies. Although a small amount of glyphosate is deadly to a plant, its human toxicity is quite low. Suggest why this powerful herbicide has little effect on humans.

Textbook Question

Give equations for the formation and hydrogenolysis of N-benzyloxycarbonyl methionine.

Textbook Question

Three peptides were obtained from a trypsin digestion of two different polypeptides. In each case, indicate the possible sequences from the given data and tell what further experiment should be carried out in order to determine the primary structure of the polypeptide.

a. polypeptide I:

1. Val-Gly-Asp-Lys

2. Leu-Glu-Pro-Ala-Arg

3. Ala-Leu-Gly-Asp

Textbook Question

Show how valine can be prepared by

d. a N-phthalimidomalonic ester synthesis.

Textbook Question

Provide a synthesis of the following amino acids using a combination of the HVZ and amination reactions.

b. Leu

Textbook Question

Show how you would synthesize the following amino acids using the Strecker amino acid synthesis.