The in vitro influence of decameric vanadate species on Na + /K +-ATPase, plasma membrane Ca 2+-ATPase (PMCA)-calcium pump and ecto-ATPase activity, using rat synaptic plasma membrane (SPM) as model system was investigated, whereas the commercial porcine cerebral cortex Na + /K +-ATPase served as a reference. The thermal behaviour of the synthesized decavanadate (V 10) has been studied by differential scanning calorimetry and thermogravimetric analysis, while the type of polyvanadate anion was identified using the IR spectroscopy. The concentration-dependent responses to V 10 of all enzymes were obtained. The half-maximum inhibitory concentration (IC 50) of the enzyme activity was achieved at (4.74 ± 1.15) × 10-7 mol/l for SPM Na + /K +-ATPase, (1.30 ± 0.10) × 10-6 mol/l for commercial Na + /K +-ATPase and (3.13 ± 1.70) × 10-8 mol/l for Ca 2+-ATPase, while ecto-ATPase is significantly less sensitive toward V 10 (IC 50 = (1.05 ± 0.10) × 10-4 mol/l) than investigated P-type ATPases. Kinetic analysis showed that V 10 inhibited Na + /K +-ATPase by reducing the maximum enzymatic velocity and apparent affinity for ATP (increasing K m value), implying a mixed mode of interaction between V 10 and P-type ATPases.