Schistosoma mansoni and Haematoloechus medioplexus: Nucleosidediphosphatase localization in tegument

Abstract

The distribution of nucleosidediphosphatase (EC 3.6.1.6) activity in the teguments of two trematodes, Haematoloechus medioplexus and Schistosoma mansoni, was determined by cytochemical methods. Enzyme activity was observed associated with the apical plasma membrane of the tegument of H. medioplexus and with the plasma membranes of the tegumental invaginations of S. mansoni. The NDPase activity is dependent on the presence on Mn 2+ ions. In addition to its ability to hydrolyze a number of nucleoside diphosphates, the tegument of H. medioplexus hydrolyzed a number of nucleoside triphosphates. The tegumental invaginations of S. mansoni represented sites where a wider variety of phosphate esters, including nucleoside mono- and triphosphates, thiamine pyrophosphate, and sodium glycerophosphate, were hydrolyzed. The hydrolysis of these latter compounds was not dependent on the presence of Mn 2+ ions, possibly indicating at least two enzyme systems associated with the tegument of S. mansoni. It is speculated that areas displaying NDPase activity represent sites of transport over which ions and molecules cross the tegument. No NDPase activity was associated with the teguments of two trematodes that reportedly display little or no ability for tegumental transport, Megalodiscus temperatus and Gorgoderina attenuata.