title: A calcium ion-dependent adenosine triphosphate pyrophosphohydrolase in plasma membrane from rat liver. Demonstration that the adenosine triphosphate analogues adenosine 5'-[betagamma-imido]triphosphate and adenosine 5'-[betagamma-methylene]-triphosphate are substrates for the enzyme.
abstract: An ATP pyrophosphohydrolase in a rat liver plasma-membrane subfraction was studied with respect to specific Ca2+ activation of the beta-phosphate bond hydrolysis. ATP and, in addition, adenosine 5'-[betagamma-imido]triphosphate and adenosine 5'-[betagamma-methlylene]triphosphate were substrates for Ca2+-stimulated enzymic hydrolysis of the beta-phosphate bond. A 15-fold activation was observed by raising the free Ca2+ concentration from 10(-7) to 10(-5) M. Mg2+ had little effect. Solubilization in 1% deoxycholate and partial purification on a sucrose density gradient resulted in a 5-fold increase in specific activity with unaltered Ca2+-stimulation pattern. The possible importance of the enzyme in Ca2+ transport is discussed.
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000031:analogs & derivatives* / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000494:pharmacology; D002462:Cell Membrane / Q000201:enzymology; D004789:Enzyme Activation / Q000187:drug effects; D008099:Liver / Q000201:enzymology*; D011755:Pyrophosphatases; D051381:Rats
chemical_list: D000255:Adenosine Triphosphate; D000251:Adenosine Triphosphatases; D011755:Pyrophosphatases; C019757:ATP pyrophosphohydrolase; D002118:Calcium