It has been reported that Ca2+ can be either stimulatory or inhibitory of the activity of Na+,K+-ATPase obtained from different sources. The aim of the present work was to study the effect of increasing concentrations of Ca2+ on Na+,K+-ATPase purified from human placenta. The temperature dependence of Na+,K+-ATPase activity and of spectral parameters of a spin label paramagnetic maleimide derivative (MSL, 2,2,6,6-tetramethylpiperidin-1-oxyl-4-maleimide) were also investigated in absence and in presence of 2 mM Ca2+. Ca2+ affects positively the enzymatic activity and this effect is evident at all temperature tested. Maleimide spectral parameters are not affected by the presence of 2 mM Ca2+ showing that the microenvironments of SH groups are not modified following ion interactions.
|Number of pages||6|
|Publication status||Published - 1992|
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