ROLE OF THE PROPHENOLOXIDASE-ACTIVATING SYSTEM IN INVERTEBRATE IMMUNITY

The melanization reaction, which is a common response to parasite entr y in invertebrate animals, especially arthropods, is due to the activi ty of an oxidoreductase, phenoloxidase. This enzyme is part of a compl ex system of proteinases, pattern recognition proteins and proteinase inhibitors constituting the so-called prophenoloxidase-activating syst em. It is proposed to be a non-self recognition system because convers ion of prophenoloxidase to active enzyme can be brought about by minus cule amounts of molecules such as lipopolysaccharide, peptidoglycan an d beta-1,3-glucans from micro-organisms. Several components of this sy stem recently have been isolated and their structure determined.