Carboxy terminal extended phytocystatins are bifunctional inhibitors of papain and legumain cysteine proteinases

FEBS Lett. 2007 Jun 26;581(16):2914-8. doi: 10.1016/j.febslet.2007.05.042. Epub 2007 May 25.


Plant legumains are cysteine proteinases putatively involved in processing endogenous proteins. Phytocystatins (PhyCys) have been described as plant inhibitors of papain-like cysteine proteinases. Some PhyCys contain a carboxy terminal extension with an amino acid motif (SNSL) similar to that involved in the inhibition of legumain-like proteins by human cystatins. The role of these carboxy terminal extended PhyCys as inhibitors of legumain-like cysteine proteinases is here shown by in vitro inhibition of human legumain and legumain-like activities from barley extracts. Moreover, site-directed mutagenesis has demonstrated that the asparagine of the SNSL motif is essential in this inhibition. We prove for first time the existence of legumain inhibitors in plants.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Cystatins / chemistry*
  • Cystatins / physiology*
  • Cysteine Endopeptidases / metabolism*
  • Cysteine Proteinase Inhibitors / chemistry
  • Cysteine Proteinase Inhibitors / physiology
  • Hordeum*
  • Models, Molecular
  • Molecular Sequence Data
  • Papain / antagonists & inhibitors*
  • Plant Proteins / chemistry
  • Plant Proteins / pharmacology
  • Protein Structure, Tertiary / physiology
  • Sequence Homology, Amino Acid


  • Cystatins
  • Cysteine Proteinase Inhibitors
  • Plant Proteins
  • Cysteine Endopeptidases
  • Papain
  • asparaginylendopeptidase