Bradykinin is a peptide released by certain organisms in response to wasp stings

Question

Bradykinin is a peptide released by certain organisms in response to wasp stings. a) Total hydrolysis gave: Phe2, Pro3, Arg2, Gly and Ser. b) Edman's analysis of the intact polypeptide PTH-arginine. c) Carboxypepsidase A treatment produced nothing significant. d) Chymotrypsin degradation gave (Arg, Gly, Phe, Pro2), (Pro, Ser, Phe) and Arg. e) Trypsin degradation of the initial peptide gave Arg and a octapeptide Treatment of the octapeptide from (e) with bromelain (which cleaves carboxyl side of Lys, Ala, Tyr, Gly) yields a tripeptide and Phe-Ser-Pro-Phe-Arg. What is the sequence of bradykinin?

Explanation / Answer

Bradykinin sequencing:

b.

Edman degrdation = PTH arginine.

So, N-terminal amino acid = Arg

f.

Pentapeptide sequence = Phe-Ser-Pro-Phe-Arg

Bromelain cleaves after Gly.

So,

Hexapeptide sequence = Gly-Phe-Ser-Pro-Phe-Arg

e.

Trypsin cleaves at the C terminal of Arg.

So, the N' and C' amino acid residues are Arg and Arg.

Hexapeptide sequence = Arg-?-?-Gly-Phe-Ser-Pro-Phe-Arg

Remaining amino acids = 2 Pro residues.

The final sequence = Sequence: N'-Arg-Pro-Pro-Gly-Phe-Ser-Pro-Phe-Arg-C'

Bradykinin:

It is a small peptide with nine amino acids.

It is a mediator of inflammatory reaction that causes vasodilation.

Sequence: N'-Arg-Pro-Pro-Gly-Phe-Ser-Pro-Phe-Arg-C'

Sequence: N'-RPPGFSPFR-C'

Empirical formula = C50H73N15O11

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