You are analyzing a short oligopeptide. Amino acid analysis indicates that the p

Question

You are analyzing a short oligopeptide. Amino acid analysis indicates that the peptide underwent

complete hydrolysis to yield the following set of amino acids:

Ala      Arg      Ser      Val      Gly      Lys      2 Met

a.         Sanger reagent (1-fluoro-2,4-dinitrobenzene) produced to products:

Dinitrophenyl-glycine Dinitrophenyl-lysine

b.         Carboxypeptidease A produced two fragments: Serine and an oligopeptide with all of the

others.

c.          Cyanogen bromide produced three oligopeptides:

GAKM                VM                     RS

d.         Chymotrypsin treatment produced no results.

e.         Trypsin treatment produced three oligopeptides: GAK                   MVMR               S

             What is the order of amino acids in this peptide chain?

Explanation / Answer

Dinitrofluorobenzene reacts with the amine group in amino acids to produce dinitrophenyl-amino acids.

In the given problem, we got Dinitrophenyl-glycine Dinitrophenyl-lysine which means that both are present at the N-terminal amino acid.

Carboxypeptidase A cleaves the amino acid present in the c-terminal that means serine is the C-terminal amino acid.

Cyanogen bromide cleaves peptide bond present on the C-terminal of amino acid methionine.

Chymotrypsin cleaves tryptophan, tyrosine, phenylalanine, and leucine. Since there is no such amino acid so we didn’t get any fragment upon chymotrypsin treatment

Trypsin cleave C-terminal of lysine and arginine amino acid

GAK                   MVMR               S

From all the above information we can conclude that

GAKMVMRS is the correct order of amino acids in the peptide

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