Evolutionary families of peptidase inhibitors

Biochem J. 2004 Mar 15;378(Pt 3):705-16. doi: 10.1042/BJ20031825.


The proteins that inhibit peptidases are of great importance in medicine and biotechnology, but there has never been a comprehensive system of classification for them. Some of the terminology currently in use is potentially confusing. In the hope of facilitating the exchange, storage and retrieval of information about this important group of proteins, we now describe a system wherein the inhibitor units of the peptidase inhibitors are assigned to 48 families on the basis of similarities detectable at the level of amino acid sequence. Then, on the basis of three-dimensional structures, 31 of the families are assigned to 26 clans. A simple system of nomenclature is introduced for reference to each clan, family and inhibitor. We briefly discuss the specificities and mechanisms of the interactions of the inhibitors in the various families with their target enzymes. The system of families and clans of inhibitors described has been implemented in the MEROPS peptidase database (http://merops.sanger.ac.uk/), and this will provide a mechanism for updating it as new information becomes available.

Publication types

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

MeSH terms

  • Biological Evolution
  • Disulfides / analysis
  • Protease Inhibitors / chemistry
  • Protease Inhibitors / classification*
  • Protease Inhibitors / pharmacology
  • Protein Conformation
  • Sequence Homology, Amino Acid
  • Terminology as Topic


  • Disulfides
  • Protease Inhibitors