ENTAMOEBA-HISTOLYTICA HM1-IMSS - HEMOGLOBIN-DEGRADING NEUTRAL CYSTEINE PROTEASES

Entamoeba histolytica HM1:IMSS traphozoites were able to utilize human hemoglobin but not hemin as a sole iron source to flow in vitro. Prot eases from crude extracts of E. histolytica degraded human, porcine, a nd bovine hemoglobins at pH 7.0. These proteolytic activities were fou nd by electrophoresis in SDS-polyacrylamide gels copolymerized with he moglobin, with apparent molecular weights of 116, 82, and 21 kDa, the 82-kDa protein being the most active protease against this substrate. The proteases were classified in the cysteine group since the activiti es were inhibited by trans-epoxysuccinylleucyiamido(4-guanidino)butane , p-hydroxymercuribenzoate, iodoacetate, and N-ethylmaleimide and acti vated with dithiothreitol. Other pathogenic strains of E. histolytica showed the same pattern of hemoglobinases. These hemoglobin-degrading proteases could be playing an important role in iron acquisition by E. histolytica. (C) 1998 Academic Press.