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Glycerol Inhibits or Uncouples the Plasma Membrane (Ca2++Mg2+)ATPase of Kidney Proximal Tubules Depending on the Ca2+ Concentration
| Content Provider | Scilit |
|---|---|
| Author | Sola-Penna, Mauro Lemos, Adriana Dos Passos Vieyra, Adalberto |
| Copyright Year | 1995 |
| Description | In this report it is shown that glycerol (0.5-10% v/v) stimulate the $C_{12}-E_{9}$-solubilized renal $(Ca^{2+}+Mg^{2+}$)ATPase in the presence of low concentrations of free $Ca^{2+}$ (< $10^{-6}$ᴍ). At 4% (v/v), the polyol decreases the $K_{0.5}$ for $Ca^{2+}$ from 1.15 to 0.22 μᴍ at the high-affinity site, and a very-high-affinity $Ca^{2+}$ component appears. This component has a $K_{0.5}$ $≤10^{-9 }$ᴍ and its maximal velocity is about one-third that of the fully activated enzyme (at 10-20 μᴍ $Ca^{2+}$), which is not affected by glycerol (21.1 and 20.2 $nmol·mg^{-1}$ $·min^{-1}$ in the absence and presence of the polyol, respectively). The low-affinity, inhibitory component of the $Ca^{2+}$ curve (50-1000 μᴍ ) is also unaffected by glycerol. With 0.07 μᴍ free $Ca^{2+}$ and soluble enzyme, the stimulatory effect of glycerol saturates at ≈10% (v/v). In contrast, with 17 μᴍ free $Ca^{2+}$, glycerol has little effect up to 10% (v/v), and then progressively inhibits ATPase activity. These data indicate that the effect of the polyol is modulated by the occupancy of the high-affinity $Ca^{2+}$ sites. In native vesicles, the stimulation promoted by low concentrations of glycerol at low concentrations of $Ca^{2+}$ is accompanied by inhibition of active $Ca^{2+}$ transport, indicating that, in these conditions, the polyol uncouples ATPase activity and ATP-driven $Ca^{2+}$ influx. |
| Related Links | http://www.degruyter.com/downloadpdf/j/znc.1995.50.issue-11-12/znc-1995-11-1217/znc-1995-11-1217.xml |
| Ending Page | 853 |
| Page Count | 9 |
| Starting Page | 845 |
| e-ISSN | 18657125 |
| DOI | 10.1515/znc-1995-11-1217 |
| Journal | Zeitschrift für Naturforschung C |
| Issue Number | 11-12 |
| Volume Number | 50 |
| Language | English |
| Publisher | Walter de Gruyter GmbH |
| Publisher Date | 1995-12-01 |
| Access Restriction | Open |
| Subject Keyword | Zeitschrift Für Naturforschung C Biochemistry and Molecular Biology Plasma Membrane (ca2++mg2+)atpase Glycerol Uncoupling of Ionic Pump Polyol Hydrophobic Interactions Journal: Zeitschrift Für Naturforschung C, Vol- 50 |
| Content Type | Text |
| Resource Type | Article |
