ABSTRACT
The number of chapters on proteinases included in this book reflects the recent upsurge of interest in the proteolytic enzymes of parasitic protozoa. From a mere trickle 10 years ago the flow of publications has now swollen such that over 100 papers on this topic have appeared in the literature in the last 2 years. Much of the earlier work on protozoan proteinases concerned free-living non-pathogenic species such as Tetrahymena and Euglena (see North, 1982). Indeed, until the late 1970s, the interest in parasite enzymes was largely confined to Entamoeba and Plasmodium, in which roles for proteinases in host tissue invasion and haemoglobin digestion, respectively, had long been anticipated. There are three main reasons for the current level of interest. First is the realization that proteolytic enzymes can have a wide variety of roles in living cells and that interference with proteolysis could affect parasite functions concerned with the host-parasite relationship and pathogenesis. Second is the development of methods, mostly adapted from procedures used to analyse mammalian proteinases, that have allowed the detection, separation and characterization of the multiple forms of proteinase that occur in parasitic protozoa. Earlier papers often referred to parasite proteinase activity in terms of a single enzyme. It is now apparent that multiple proteinases are the rule, and one of the challenges of proteinase research is to unravel the complexity by identifying individual enzymes and establishing their respective properties and function. Third, and of direct relevance to the development of drugs, is the availability of a range of peptide derivatives which have been designed to inhibit specific proteinases. These now offer the parasitologist the opportunity to use reagents which may selectively inhibit the protozoan proteinases. Much of the recent work has been stimulated by the idea that the proteinases will prove to be appropriate targets for antiparasite drugs.
