How many peptide fragments can be generated from the complete digestion of the polypeptide
AGRCDKCQANRSLMNF with trypsin?
1.6
2.4
3.3
4.2

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Trypsin Digestion: How It Works

Trypsin is a proteolytic enzyme (protease) that specifically cleaves peptide bonds at the C-terminal side of two basic amino acids:

• Arginine (R)

• Lysine (K)

However, trypsin does not cleave if the basic residue is followed by Proline (P).

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Given Polypeptide Sequence:

AGRCDKCQANRSLMNF

Let’s identify all the cleavage sites:

1. A–G–R → Cut after R

2. C–D–K → Cut after K

3. Q–A–N–R → Cut after R

These are the positions where trypsin would cleave:

• After the first R (position 3)

• After the K (position 7)

• After the second R (position 11)

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Resulting Peptide Fragments:

After cutting at those three points, the polypeptide will break into 4 fragments:

1. A–G–R

2. C–D–K

3. C–Q–A–N–R

4. S–L–M–N–F

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Answer: 4 Peptide Fragments

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Why It Matters in Proteomics

Understanding enzyme specificity helps in:

• Protein sequencing

• Mass spectrometry analysis

• Peptide mapping and identification

Trypsin is widely used in research for its predictable cleavage pattern, making it easier to analyze complex protein samples.

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🔬 Conclusion

Trypsin cleaves at the C-terminal side of arginine and lysine residues. When applied to the polypeptide AGRCDKCQANRSLMNF, it produces 4 distinct peptide fragments—making option 2 the correct answer.