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Ectonucleotide diphosphohydrolase activities in Entamoeba histolytica
F S Barros1, L F De Menezes, A A Pinheiro
1Departamento de Bioquímica Médica, Instituto de Biofísica Carlos Chagas Filho, Instituto de Microbiologia Professor Paulo de Góes, Universidade Federal do Rio de Janeiro, RJ, Rio de Janeiro, CCS, Bloco H, Cidade Universitária, Ilha do Fundã.
Archives of Biochemistry and Biophysics
|March 4, 2000
Summary
Living Entamoeba histolytica cells can break down extracellular ATP, with activity significantly boosted by magnesium ions. This ecto-ATPase activity varies between Entamoeba species and is influenced by galactose.
Area of Science:
- Biochemistry
- Cell Biology
- Parasitology
Background:
- Extracellular ATP hydrolysis is crucial for cellular processes.
- Understanding ecto-ATPase activity in parasitic protozoa like Entamoeba histolytica is important for elucidating host-parasite interactions.
Purpose of the Study:
- To investigate the ecto-ATPase activity of living Entamoeba histolytica cells.
- To characterize the factors influencing this activity, including divalent metal ions and pH.
- To compare ecto-ATPase activity across different Entamoeba species.
Main Methods:
- Assessing ATP hydrolysis in intact, viable Entamoeba histolytica cells.
- Dose-response studies with magnesium chloride (MgCl2).
- Enzyme inhibition assays and kinetic analysis (K(m) determination).
- Comparative analysis of ecto-ATPase activity in E. histolytica, E. moshkovskii, and a non-pathogenic E. histolytica strain.
- Investigating the effect of galactose on ecto-ATPase activity.
Main Results:
- Entamoeba histolytica exhibits ecto-ATPase activity, significantly enhanced by MgCl2 in a dose-dependent manner.
- The activity is also stimulated by MnCl2 and CaCl2, but inhibited by FeCl3.
- Mg2+-dependent activity increases with pH, while Mg2+-independent activity is pH-stable.
- Kinetic analysis revealed distinct apparent K(m) values for basal and Mg2+-dependent ATP hydrolysis.
- Pathogenic Entamoeba histolytica showed higher ATP hydrolysis rates than non-pathogenic and free-living species.
- Galactose specifically stimulated the Mg2+-dependent ecto-ATPase activity.
Conclusions:
- Living Entamoeba histolytica cells possess significant ecto-ATPase activity, modulated by divalent cations and pH.
- The characterized ecto-ATPase activity is specific for ATP and ADP, with distinct kinetic properties.
- Species-specific differences in ecto-ATPase activity may correlate with pathogenicity.
- The stimulatory effect of galactose suggests a potential role for lectin-mediated ecto-ATPase regulation in amebiasis pathogenesis.