Evidence for phospholipases from Trypanosoma cruzi active on phosphatidylinositol and inositolphosphoceramide

The lipid moiety in the glycosylphosphatidylinositol anchors of glycoprotei ns of Trypanosoma cruzi consists of an alkylacylglycerol, a lysoalkylglycer ol or a ceramide. Previously, we showed that the inositolphosphoceramides ( IPCs) are the major components in the precursor inositolphospholipids of ep imastigote and trypomastigote forms. Using H-3-labelled subfractions of IPC , phosphatidylinositol (PI) and glycoinositolphospholipids (GIPLs) as subst rates with a cell-free system, we now demonstrate the association of at lea st five enzyme activities with the trypanosomal membranous particulate mate rial. These include: phospholipase A(1) and phospholipase A(2), enzymes tha t release free fatty acid from the PI and GIPLs; an acyltransferase respons ible for the acylation of the generated monoacyl or monoalkylglycero-lipids with endogenous unlabelled fatty acid; two activities of phospholipase C, one releasing ceramide from IPC and the other alkylacylglycerol, alkylglyce rol or diacylglycerol from PI. The neutral lipids were also generated on in cubation of the GIPLs. The phospholipase C activities were inhibited by p-c hloro-mercuriphenylsulphonic acid, as reported for other PI phospholipases C. An IPC-fatty-acid hydrolase, releasing fatty acid from the labelled IPC, was also observed. The enzyme activities reported in the present study may be acting in remodelling reactions leading to the anchor of the mature gly coproteins of T. cruzi.