Ca2+/Mg(2+)-dependent ATPase activity in Hymenolepis diminuta mitochondria

Area of Science:

• Biochemistry
• Parasitology
• Molecular Biology

Background:

• Mitochondrial membranes of the rat intestinal cestode Hymenolepis diminuta possess ATPase activity.
• Understanding cestode ATP hydrolysis is crucial for developing targeted antiparasitic strategies.

Purpose of the Study:

• To investigate the activation of ATP hydrolysis by divalent cations (Ca2+ and Mg2+) in Hymenolepis diminuta mitochondrial membranes.
• To characterize the kinetic properties of cation-dependent ATPase activity and compare it with mammalian ATPases.

Main Methods:

• Enzyme kinetics studies using Lineweaver-Burk plots to determine Km and Vmax values for Ca2+ and Mg2+ dependent ATP hydrolysis.
• Assays to test the effects of other cations (Na+, K+), inhibitors (ouabain, ruthenium red), and membrane modifiers (Triton X-100, neuraminidase, concanavalin A).
• Evaluation of the hydrolysis of other nucleoside triphosphates and the impact of anthelmintics.

Main Results:

• Ca2+ and Mg2+ activated ATP hydrolysis in a concentration-dependent manner, with Ca2+ being more potent and Mg2+ more effective.
• Kinetic parameters (Km, Vmax) were determined for both Ca2+- and Mg2+-dependent activities.
• The enzyme activity was not affected by Na+, K+, ouabain, ruthenium red, neuraminidase, concanavalin A, or common anthelmintics, suggesting distinct properties from mammalian ATPases.
• Triton X-100 was optimal for solubilizing the enzyme activities.
• Ca2+ and Mg2+ also hydrolyzed other nucleoside triphosphates.

Conclusions:

• Hymenolepis diminuta mitochondrial membranes exhibit distinct Ca2+- and Mg2+-dependent ATPase activities.
• These cestode ATPases differ significantly from their mammalian counterparts in terms of cation activation, kinetics, and inhibitor sensitivity.
• The findings provide insights into cestode bioenergetics and potential targets for antiparasitic drug development.