ISSN:
1573-4919
Keywords:
regucalcin
;
calcium-binding protein
;
(Ca2+−Mg2+)-ATPase
;
plasma membrane
;
rat liver
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Chemistry and Pharmacology
,
Medicine
Notes:
Abstract The effect of various metals and regucalcin, a calcium-binding protein isolated from rat liver cytosol, on (Ca2+−Mg2+)-ATPase activity in the plasma membranes of rat liver was investigated. Of various metals (Zn2+, Cu2+, Ni2+, Mn2+, Co2+ and Al3+; 100 μM as a final concentration), Mn2+ and Co2+ increased markedly (Ca2+−Mg2+)-ATPase activity, while other metals had no effect. When Ca2+ was not added into enzyme reaction mixture, Mn2+ and Co2+ (25–100 μM) did not significantly increase the enzyme activity, indicating that heavy metals act on Ca2+-stimulated phosphorylation of the enzyme. Meanwhile, regucalcin (0.25–1.0 μM) caused a remarkable elevation of (Ca2+−Mg2+)-ATPase activity. This increase was not inhibited by the presence of 100 μM vanadate, although the effects of Mn2+ and Co2+ (100 μM) were inhibited by vanadate. Also, the inhibition of the Mn2+ and Co2+ effects by vanadate was not seen in the presence of regucalcin. Moreover, regucalcin (0.5 μM) increased significantly the enzyme activity in the absence of Ca2+. This effect of regulcalcin was not altered by increasing concentrations of Ca2+ added, indicating that the regucalcin effect does not depend on Ca2+. The present results suggest that regucalcin activates directly (Ca2+−Mg2+)-ATPase in liver plasma membranes, and that the activation is not involved in the Ca2+-dependent phosphorylation of the enzyme.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00929209
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