Question

Problem Title: Peptide Sequencing (Intro to Biochemichemistry)

#1:

Hydrolysis of dodecapeptide P with the enzyme trypsin affords the following fragments: Pro-Thr-Phe-Phe-Tyr-Ala-Arg, Asp-Asn-Arg, His-Arg.

Hydrolysis with chymotrypsin yields: Phe, Tyr, His-Arg-Pro-Thr-Phe, Ala-Arg-Asp-Asn-Arg.

What is the amino acid sequence of P? ___

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#2:

Hydrolysis of nonapeptide P with the enzyme trypsin affords the following fragments: Glu-Ser-Arg, Glu-Tyr-Ser-Phe-Ala-Arg.

Hydrolysis with chymotrypsin yields: Glu-Tyr, Ser-Phe, Ala-Arg-Glu-Ser-Arg.

What is the amino acid sequence of P? ___

Answer 1

#1. Peptide P has is a 12mer (Dodeca) peptide.

Tyrpsin cleaves the peptide chain at Lysine and Arginine residues from C-terminal. Thus the residues obtained by trypsin hydrolysis are as follows:

Pro-Thr-Phe-Phe-Tyr-Ala-Arg, Asp-Asn-Arg, His-Arg

Chymotrypsin cleaves the peptide chain at aromatic residues viz. Tyrosine, Phenylalanine and Tryptophan from C-terminal. Thus the residues obtained by chymotrypsin hydrolysis are as follows:

Phe, Tyr, His-Arg-Pro-Thr-Phe, Ala-Arg-Asp-Asn-Arg

Hence the most probable amino acid sequence for peptide P will be:

His-Arg-Pro-Thr-Phe-Phe-Tyr-Ala-Arg-Asp-Asn-Arg.

#2. Peptide P has is a 9mer (Nona) peptide.

Tyrpsin cleaves the peptide chain at Lysine and Arginine residues from C-terminal. Thus the residues obtained by trypsin hydrolysis are as follows:

Glu-Ser-Arg, Glu-Tyr-Ser-Phe-Ala-Arg

Chymotrypsin cleaves the peptide chain at aromatic residues viz. Tyrosine, Phenylalanine and Tryptophan from C-terminal. Thus the residues obtained by chymotrypsin hydrolysis are as follows:

Glu-Tyr, Ser-Phe, Ala-Arg-Glu-Ser-Arg

Hence the most probable amino acid sequence for peptide P will be:

Glu-Tyr-Ser-Phe-Ala-Arg-Glu-Ser-Arg