Occurrence and properties of proteases in plant latices.

Proteases appear to play key roles in the regulation of biological processes in plants, such as the recognition of pathogens and pests and the induction of effective defence responses. On the other side these enzymes are able to activate protease-activated receptors (PARs) and in that way to act as agents with pharmacological and toxicological significance. An important source of plant proteases used in traditional medicine and industry is latex. Over 110 latices of different plant families are known to contain at least one proteolytic enzyme. Most of them belong to the cysteine or serine endopeptidases family and only one to the aspartatic endopeptidases family. This review focuses on the characterization of proteases found in latices of several plant families (Apocynaceae, Asclepiadaceae, Asteraceae, Caricaceae, Convolvulaceae, Euphorbiaceae, Moraceae), and summarizes the known chemical and biological properties of the isolated proteases as well as their importance in pharmacology and toxicology.