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Peptide macrocyclization by a bifunctional endoprotease.

Kalia Bernath-Levin1, Clark Nelson2, Alysha G Elliott3

  • 1The University of Western Australia, School of Chemistry and Biochemistry, 35 Stirling Highway, Crawley, Perth 6009, Australia; ARC Centre of Excellence in Plant Energy Biology, 35 Stirling Highway, Crawley, Perth 6009, Australia.

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Summary
This summary is machine-generated.

Sunflower trypsin inhibitor 1 (SFTI-1) is macrocyclized by asparaginyl endopeptidase (AEP). This study confirms AEP

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Area of Science:

  • Biochemistry
  • Plant Science
  • Molecular Biology

Background:

  • Proteases typically cleave peptide bonds.
  • Some proteases can also ligate peptides under specific conditions.
  • Sunflower seeds contain the macrocyclic peptide sunflower trypsin inhibitor 1 (SFTI-1).

Purpose of the Study:

  • To provide direct evidence for asparaginyl endopeptidase (AEP) in SFTI-1 maturation.
  • To investigate the mechanism of SFTI-1 excision and macrocyclization.
  • To explore the potential of plant endopeptidases in stabilizing bioactive peptides.

Main Methods:

  • Development of an in situ assay using (18)O-water to track peptide modification.
  • Production of recombinant plant asparaginyl endopeptidases (AEPs) in E. coli.
  • Characterization of enzymatic activity, including cleavage and transpeptidation reactions.

Main Results:

  • Demonstration of SFTI-1 excision and simultaneous macrocyclization from its precursor in situ.
  • Identification of a breakdown pathway that can mask the inefficiency of the in situ reaction.
  • Confirmation that a recombinant jack bean AEP can catalyze both cleavage and cleavage-dependent intramolecular transpeptidation to form SFTI-1.

Conclusions:

  • Asparaginyl endopeptidase (AEP) directly catalyzes the excision and macrocyclization of SFTI-1.
  • Plants like sunflower and jack bean may utilize ligating endoproteases for stabilizing bioactive peptides.
  • The evolution of ligating endoproteases offers a mechanism for generating stable, functional peptides in plants.