The possibility that Ca(2+)-ATPase from the plasma membrane-rich fraction of bovine parotid gland is ecto-Ca(2+)-dependent nucleoside triphosphatase.
1. Parotid plasma membrane nonpump low-affinity Ca(2+)-ATPase, which possesses high-affinity (Ca2+ + Mg2+)-ATPase activity, was characterized. 2. Purified Ca(2+)-ATPase hydrolyzed the nucleoside triphosphates, GTP, ITP, CTP, UTP, TTP (67-93% of ATP) and nucleoside diphosphates, ADP, GDP, IDP, CDP, TDP (12-40% of ATP) but not AMP and p-NPP. 3. The maximum activities of Ca(2+)- and (Ca2+ + Mg2+)-ATPases were obtained in the presence of 1 mM and 0.13 microM Ca2+, respectively. 4. The Km values for Ca2+ in Ca(2+)- and (Ca2+ + Mg2+)-ATPases were 0.2 mM and 22 nM, respectively. 5. The activities of both Ca(2+)- and (Ca2+ + Mg2+)-ATPases were found in the right-side-out-vesicles obtained from the plasma membrane-rich fraction. 6. These features suggest that Ca(2+)-ATPase is an ecto-Ca(2+)-dependent nucleoside triphosphatase.
Sato
J
J
Department of Biochemistry, Nihon University School of Dentistry at Matsudo, Chiba, Japan.
Matsukawa
R
R
Takiguchi
H
H
D000818:Animals; D017301:Ca(2+) Mg(2+)-ATPase / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D000252:Calcium-Transporting ATPases / Q000302:isolation & purification / Q000378:metabolism*; D002417:Cattle; D002462:Cell Membrane / Q000201:enzymology*; D006868:Hydrolysis; D007700:Kinetics; D009711:Nucleotides / Q000378:metabolism*; D010306:Parotid Gland / Q000201:enzymology*; D013379:Substrate Specificity
D009711:Nucleotides; D017301:Ca(2+) Mg(2+)-ATPase; D000252:Calcium-Transporting ATPases; D002118:Calcium