title: Plant cysteine proteases that evoke itch activate protease-activated receptors.
abstract: BACKGROUND
  Bromelain, ficin and papain are cysteine proteases from plants that produce itch upon injection into skin. Their mechanism of action has not been considered previously.
  
  
  OBJECTIVE
  To determine the mechanism by which these proteases function.
  
  
  METHODS
  The ability of these proteases to activate protease-activated receptors was determined by ratiometric calcium imaging.
  
  
  RESULTS
  We show here that bromelain, ficin and papain activate protease-activated receptors 2 and 4.
  
  
  CONCLUSIONS
  Bromelain, ficin and papain function as signalling molecules and activate protease-activated receptors. Activation of these receptors is the likely mechanism by which these proteases evoke itch.
authors.affiliation: Massachusetts General Hospital Cutaneous Biology Research Center, Charlestown, MA 02129, U.S.A.
authors.forename: V B
authors.initials: VB
authors.lastname: Reddy
authors.forename: E A
authors.initials: EA
authors.lastname: Lerner
mesh_terms: D001963:Bromelains / Q000494:pharmacology*; D002118:Calcium / Q000032:analysis; D004789:Enzyme Activation / Q000187:drug effects*; D005361:Ficain / Q000494:pharmacology*; D006801:Humans; D010206:Papain / Q000494:pharmacology*; D010936:Plant Extracts / Q000494:pharmacology; D011537:Pruritus / Q000139:chemically induced / Q000201:enzymology; D044462:Receptors, Proteinase-Activated / Q000378:metabolism*
chemical_list: D010936:Plant Extracts; D044462:Receptors, Proteinase-Activated; D001963:Bromelains; D010206:Papain; D005361:Ficain; D002118:Calcium