PROTEOLYTIC ACTIVITY IN EXTRACTS OF ENTAMOEBA-INVADENS AND ENTAMOEBA-HISTOLYTICA - A COMPARATIVE-STUDY

Two species of amoebae: Entamoeba invadens and Entamoeba histolytica a re potentially invasive in reptiles and certain primates, respectively . Since proteinases may be involved in pathogenic mechanisms (tissue n ecrosis), at least in E. histolytica, it was of interest to compare th eir proteases. We compared the sensitivity of proteolytic activity in extracts of both species of amoebae to pH, temperature, and proteinase inhibitors of different catalytic classes. Proteinases in extracts of E. invadens were mainly inhibited in the presence of chelating agents , in contrast to the partial or complete activation for proteinases of E. histolytica. The pH-dependence curves for both types of extracts w ere also different. When hide powder azure was used as a substrate, ex tracts of E. histolytica showed a maximum of activity at pH 7 and a sh oulder at pH 5, while extracts of E. invadens only showed a maximum at pH 7.4. With azocasein as substrate, extracts of E. invadens had two maxima of activity at pH 6 and 7.4, while extracts of E. histolytica h ad a maximum at pH 6 and a shoulder at pH 7.4. The temperature optimum for the digestion of azocasein was 60 degrees C for extracts of E. in vadens and E. histolytica, but proteolytic activity in the latter was more resistant to temperature. Analysis of lysates from both species o f amoebae by substrate-gel electrophoresis, also showed marked differe nces in the observed lysis zones. E. histolytica showed six hydrolysis zones at with relative molecular masses of 66, 58, 42, 31, 28, and 23 kDa; and E. invadens showed only two zones, with relative molecular m asses of 52 and 45 kDa. We conclude that although both species of amoe bae contain mainly cysteine proteinases, the enzymes contained in both types of cells are different.