Uploaded by Mahmud Ismail

Edman degredation

Subject: Biochemistry and Molecular Biology
Course Name: Protein Technology
Course no.: BMB-305
Submitted By:
Name: MD. Shakil Ahmed
Submitted To:
Roll: 1810425117
Name: Md Nuruzzaman
Session: 2017-18
(Assistant professor)
Year: Third
Department of. Biochemistry and
Department of. Biochemistry and
Molecular Biology
Molecular Biology
Rajshahi University,
Rajshahi University,
Edman degradation
Edman degradation, developed by Pehr Edman, is a method of sequencing
amino acids in a peptide. In this method, the amino-terminal residue is labeled
and cleaved from the peptide without disrupting the peptide bonds between
other amino acid residues. The Edman degradation sequentially removes one
residue at a time from the amino end of a peptide.
The Edman degradation process are as follows,
Suppose that the protein is: Ala-Gly-Asp-Phe-Arg-Gly
We expose the peptide to phenyl isothiocyanate. This molecule reacts with the
uncharged terminal α- amino group of the peptide to form a
phenylthiocarbamoyl derivative. Then, under mildly acidic conditions, a cyclic
derivative of the terminal amino acid is liberated, which leaves an intact
peptide shortened by one amino acid, which can be identified by
chromatographic procedures. Furthermore, the amino acid composition of the
shortened peptide:
(Arg , Asp, Gly2, Phe)
can be compared with that of the original peptide:
(Ala, Arg, Asp, Gly2, phe).
The difference between these analyses is one alanine residue, which shows that
alanine is the amino-terminal residue the original peptide. The Edman
procedure can then be repeated on the shortened peptide. The amino acid
analysis after the second round of degradation is,
(Arg, Asp, Gly, Phe)
showing that the second residue from the amino end is glycine. This conclusion
can be confirmed by chromatographic identification of PTH-glycine obtained
in the second round of the Edman degradation.
Three more rounds of the Edman degradation will reveal the complete
sequence of the original peptide.