A structure for the octapeptide is to be proposed from the following observations. a) It shows the composition Asp, Gly2, Leu, Phe, Pro2, Val on amino acid analysis. b) Edmund analysis showed Glycine as the N-terminal group and Leucine as the C-terminal group. C) The following fragments are produced during acidic hydrolysis Val-Pro-Leu, Gly, Gly-Asp-Phe-Pro, Phe-Pro-Val. Concept introduction: The aminoacid sequence of a peptide can be arrived by arranging the fragments produced during hydrolysis in a line one below the other such that N-terminal amino acid is at the left and C-terminal acid at the right and identifying the overlapping amino acids. To propose: A structure for the octapeptide which shows the reactions given.

Question

Somatostatin is a tetradecapeptide of the hypothalamus that inhibits the release of pituitary growth hormone. Its amino acid sequence has been determined by a combination of Edman degradations and enzymic hydrolysis experiments. On the basis of the following data, deduce the primary structure of somatostatin: 1. Edman degradation gave PTH-Ala. 2. Selective hydrolysis gave peptides having the following indicated sequences: Phe-Trp Thr-Ser-Cys Lys-Thr-Phe Thr-Phe-Thr-Ser-Cys Asn-Phe-Phe-Trp-Lys Ala-Gly-Cys-Lys-Asn-Phe 3. Somatostatin has a disulfide bridge.

Answer 1

Question

Chapter 26.SE, Problem 54AP

Interpretation Introduction

Interpretation:

A structure for the octapeptide is to be proposed from the following observations. a) It shows the composition Asp, Gly2, Leu, Phe, Pro2, Val on amino acid analysis. b) Edmund analysis showed Glycine as the N-terminal group and Leucine as the C-terminal group. C) The following fragments are produced during acidic hydrolysis Val-Pro-Leu, Gly, Gly-Asp-Phe-Pro, Phe-Pro-Val.

Concept introduction:

The aminoacid sequence of a peptide can be arrived by arranging the fragments produced during hydrolysis in a line one below the other such that N-terminal amino acid is at the left and C-terminal acid at the right and identifying the overlapping amino acids.

To propose:

A structure for the octapeptide which shows the reactions given.

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Somatostatin is a tetradecapeptide of the hypothalamus that inhibits the release of pituitary growth hormone. Its amino acid sequence has been determined by a combination of Edman degradations and enzymic hydrolysis experiments. On the basis of the following data, deduce the primary structure of somatostatin: 1. Edman degradation gave PTH-Ala. 2. Selective hydrolysis gave peptides having the following indicated sequences: Phe-Trp Thr-Ser-Cys Lys-Thr-Phe Thr-Phe-Thr-Ser-Cys Asn-Phe-Phe-Trp-Lys Ala-Gly-Cys-Lys-Asn-Phe 3. Somatostatin has a disulfide bridge.

Using the information below, determine the amino acid sequence of the peptide, and explain how your structure is consistent with each piece of information. Complete hydrolysis by 6 M HCl at 110°C followed by amino acid analysis indicated the presence of Gly, Leu, Phe, and Tyr in a 2:1:1:1 molar ratio. Treatment of the peptide with1-fluoro-2,4-dinitrobenzene followed by complete hydrolysis and chromatography indicated the presence of the 2,4-dinitrophenyl derivative of tyrosine. No free tyrosine could be found. Complete digestion of he peptide with pepsin (which cleaves on the amino side of aromatic residues) followed by chromatography yielded a dipeptide containing Phe and Leu and a tripeptide containing Tyr and Gly in a 1:2 ratio.

Determine the amino acid sequence of a polypeptide from the following data:Acid-catalyzed hydrolysis gives Ala, Arg, His, 2 Lys, Leu, 2 Met, Pro, 2 Ser, Thr, and Val.Carboxypeptidase A releases Val.Edman’s reagent releases PTH-Leu.Treatment with cyanogen bromide gives three peptides with the following amino acid compositions:1. His, Lys, Met, Pro, Ser 2. Thr, Val 3. Ala, Arg, Leu, Lys, Met, Ser