Question

The following decapeptide composition resulted from an amino acid analysis:

Asn, Glu, Trp, 2 Thr, Met, Leu, Ala, His, Phe

1. Pepsin (cleaves on N-side of aromatics) yielded a tripeptide composition (Trp, Leu, Glu), a hexapeptide, and a free Thr.

2. Chymotrypsin (cleaves C-side of aromatics) treatment gave dipeptide composition (Thr, Trp), tripeptide composition (Glu, Phe, Leu), and a pentapeptide. The first amino of the pentapeptide has a secondary alcohol.

3. Elastase (cleaves C-side of Gly and Ala) resulted in a free Asn and a nanopeptide.

4. CNBr (cleaves C-side of Met) treating of the whole peptide resulted in a dipeptide and an octapeptide.

5. V8 protease (cleaves C-side of Glu and Asp) resulted in tripeptide and a heptapeptide.

With the given treatments, what is the amino acid squence for the polypeptide chain?

Answer 1

1) pepsin leads to result that N-terminus of decapeptaide is Thr and of tripeptide is Trp and of hexapeptide Phe.

2) Chymo trypsin leads to result that dipeptide is Thr-Trp and C-terminus of tripeptide is Phe and N-termiuns of pentapeptide is Thr.

3) Elastase (cleaves C-side of Gly and Ala) resulted in a free Asn and a nanopeptide. therefore C-terminus of decapeptide is Ala-Asn.

4. CNBr (cleaves C-side of Met) treating of the whole peptide resulted in a dipeptide and an octapeptide.

5. V8 protease (cleaves C-side of Glu and Asp) resulted in tripeptide and a heptapeptide.

therefore

the peptide is Thr-Trp-Glu-Leu-Phe-Thr-His-Met-Ala-Asn