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

The parasitic protozoan Entamoeba histolytica is able to invade human tissues by secreting proteolytic enzymes. This secretion is regulated by inositol phosphate-mediated Ca2+ release from internal stores. To further investigate the inositol phosphate metabolism of Entamoeba histolytica four putative inositol phosphate kinase genes (ehipk1-4) were identified and their expression analyzed by real-time quantitative PCR using RNA of trophozoites. Furthermore inositol phosphate kinase EhIPK1 was recombinantly expressed, purified and enzymatically characterized. Its main activity is the conversion of InsP6 to 5PP-Ins(1,2,3,4,6)P5, one of the main inositol phosphates found in Entamoeba histolytica. Remarkably, EhIPK1 possesses several additional enzymatic activities, e.g. the phosphorylation of the Ca2+-releasing second messenger Ins(1,4,5)P3.We were able to identify several compounds with inhibitory potential against EhIPK1. 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.

An inositol phosphate kinase from Entamoeba histolytica was identified. It possesses enzymatic activity to generate one of the main inositol phosphates found in this protozoan.101Highlights► Four inositol phosphate kinase genes from Entamoeba histolytica were identified. ► A recombinant inositol phosphate kinase was enzymatically characterized. ► This enzyme generates one of the main inositol phosphates found in this protozoan. ► It also converts the Ca2+-releasing second messenger Ins(1,4,5)P3 to Ins(1,4,5,6)P4.