Peptide backbone cleavage by α-amidation is enhanced at methionine residues

Research output: Contribution to journalResearch articleContributedpeer-review


  • Michael Hellwig - , Chair of Food Chemistry, TUD Dresden University of Technology (Author)
  • Katja Löbmann - , TUD Dresden University of Technology (Author)
  • Tom Orywol - , TUD Dresden University of Technology (Author)


Cleavage reactions at backbone loci are one of the consequences of oxidation of proteins and peptides. During α-amidation, the Cα-N bond in the backbone is cleaved under formation of an N-terminal peptide amide and a C-terminal keto acyl peptide. On the basis of earlier works, a facilitation of α-amidation by the thioether group of adjacent methionine side chains was proposed. This reaction was characterized by using benzoylmethionine and benzoyl alanylmethionine as peptidemodels. The decomposition of benzoylated amino acids (benzoyl-methionine, benzoyl-alanine, and benzoyl-methionine sulfoxide) to benzamide in the presence of different carbohydrate compounds (reducing sugars, Amadori products, and reductones) was studied during incubation for up to 48h at 80 °C in acetate-buffered solution (pH 6.0). Small amounts of benzamide (0.3-1.5mol%) were formed in the presence of all sugars and from all benzoylated species. However, benzamide formation was strongly enhanced, when benzoyl methionine was incubated in the presence of reductones and Amadori compounds (3.5-4.2mol%). The reaction was found to be intramolecular, because α-amidation of a similar 4-methylbenzoylated amino acid was not enhanced in the presence of benzoyl-methionine and carbohydrate compounds. In the peptide benzoyl-alanyl-methionine, α-amidation at themethionine residue is preferred over α-amidation at the benzoyl peptide bond. We propose here a mechanism for the enhancement of α-amidation at methionine residues.


Original languageEnglish
Pages (from-to)17-23
Number of pages7
JournalJournal of peptide science
Issue number1
Publication statusPublished - Jan 2015

External IDs

PubMed 25420700
ORCID /0000-0001-8528-6893/work/142256528



  • Amadori product, Backbone cleavage, Carbohydrate, Methionine, Protein oxidation, Reductone, α-amidation