A novel Entamoeba histolytica inositol phosphate kinase catalyzes the formation of 5PP-Ins(1,2,3,4,6)P5

Abstract The parasitic protozoan Entamoeba histolytica is able to invade human tissues by secreting proteolytic enzymes. This secretion is regulated by inositol phosphate-mediated Ca 2+ release from internal stores. To further investigate the inositol phosphate metabolism of Entamoeba histolytica four putative inositol phosphate kinase genes ( ehipk 1-4) were identified and their expression analyzed by real-time quantitative PCR using RNA of trophozoites. Furthermore inositol phosphate kinase EhIPK 1 was recombinantly expressed, purified and enzymatically characterized. Its main activity is the conversion of InsP 6 to 5PP-Ins(1,2,3,4,6)P 5 , one of the main inositol phosphates found in Entamoeba histolytica . Remarkably, Eh IPK1 possesses several additional enzymatic activities, e.g . the phosphorylation of the Ca 2+ -releasing second messenger Ins(1,4,5)P 3 .We were able to identify several compounds with inhibitory potential against Eh IPK1. Because of the important role of inositol phosphates in the invasion of human tissues by Entamoeba histolytica , inositol phosphate metabolizing enzymes are interesting targets for novel therapeutic approaches.