An initial characterization of the proteolytic enzymes secreted by the adult stage of the human hookwormNecator americanus

Abstract

SUMMARYThe proteolytic activities present in adultNecator americanusexcretory–secretory products have been assessed using biologically relevant, naturally occurring substrates (haemoglobin and fibrinogen) and a number of synthetic fluorogenic and chromogenic substrates. One broad peak of activity was observed against haemoglobin in the pH range 5 to 7, with maximum activity at pH 6·6, while fibrinogenolytic activity was shown to be greater at pH 3·5. Inhibition studies against haemoglobin, fibrinogen and synthetic substrates using a battery of appropriate protease inhibitors indicated the presence of a mixture of aspartyl, cysteinyl and serine proteases. Metal ion (Ca2+, Zn2+and Fe2+) stimulation was demonstrated, with stimulation by Zn2+being the most marked. These results are discussed in the context of recent developments in the field of parasite proteolytic enzymes, where they have been suggested as targets for immuno- and chemotherapy.