Journal
ARCHIVES OF BIOCHEMISTRY AND BIOPHYSICS
Volume 495, Issue 1, Pages 62-66Publisher
ELSEVIER SCIENCE INC
DOI: 10.1016/j.abb.2009.12.021
Keywords
Ca2+ pump; Ca2+ ATPase; Plasma membrane; PMCA; P-ATPase
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Funding
- Universidad de Buenos Aires [B09]
- CONICET PIP [112-200801-02022]
- ANPCyT Prestamo BID [PICT 15-25965]
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The plasma membrane Ca2+ ATPase catalyzed the hydrolysis of ATP in the presence of millimolar concentrations of EGTA and no added Ca2+ at a rate near 1.5% of that attained at saturating concentrations of Ca2+. Like the Ca-dependent ATPase, the Ca-independent activity was lower when the enzyme was auto-inhibited, and increased when the enzyme was activated by acidic lipids or partial proteolysis. The ATP concentration dependence of the Ca2+-independent ATPase was consistent with ATP binding to the low affinity modulatory site. In this condition a small amount of hydroxylamine-sensitive phosphoenzyme was formed and rapidly decayed when chased with cold ATP. We propose that the Ca2+-independent ATP hydrolysis reflects the well known phosphatase activity which is maximal in the absence of Ca2+ and is catalyzed by E-2-like forms of the enzyme. In agreement with this idea pNPP, a classic phosphatase substrate was a very effective inhibitor of the ATP hydrolysis. (C) 2009 Elsevier Inc. All rights reserved.
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