Synthetic Monoacylphospholipids as Reactivators of the Calcium‐Dependent ATPase of Enzymatically Delipidated Sarcoplasmic Membranes

Publisher Website
Google Scholar
Abstract
The reactivating effect of synthetic analogues of natural lysophosphatidylcholines, acyldeoxyglucerophosphocholines, with acyl chain lengths between C10-C18 on enzymatically delipidated [rabbit skeletal muscle] sarcoplasmic membranes was analyzed. Ca2+ dependent ATPase is fully restored by myristolydeoxyglucerophosphocholine. The restoring effect of deoxyglycerophosphocholines declines when the length of the saturated acyl chain becomes shorter or longer. In contrast to the weakly effective palmitoyldeoxyglcerophosphocholine, its cis-9-mono unsaturated analogue olexyldeoxyglycerophosphocholine was a highly effective reactivating compound. The transfer of the terminal phosphate residue of ATP to the transport protein and the phosphate exchange between ADP and ATP displays the same dependence on the acyl chain length of the deoxyglycerophosphocholines. In contrast to the ATPase activity the ATP-supported phosphoryltransfer reactions can only partially be restored. A significant restoration of the phosphorylation of the protein by PI could be acheived with none of the deoxyglycerophosphocholines. Below 23.degree. C the apparent activation energy of the Ca2+-dependent ATPase increases with increasing chain length of the deoxyglycerophosphocholines while above 23.degree. C the activation energies were identical for all restituted preparations.