Characterization of the divalent cation activated adenosine triphosphatase from the membrane of the cardiac cell ofModiolus demissus demissus

✍ Scribed by Watts, John A. ;Pierce, Sidney K.

• Publisher: John Wiley and Sons
• Year: 1978
• Tongue: English
• Weight: 465 KB
• Volume: 204
• Category: Article
• ISSN: 0022-104X
• DOI: 10.1002/jez.1402040105

✦ Synopsis

Cell-surface membranes from Modiolus dernissus possess divalent cation stimulated adenosine triphosphatase (ATPase) activity. The ATPase activity was stimulated by Ca2+ and to a lesser extend by Mgz+ in the presence of 3 mM ATP. When Ca2+ and Mg2+ were combined in the sea-water ratio of 1:5, constant ATPase activity, intermediate between that in the presence of CaZ+ or Mg2+ alone, was observed from 10:50 mM to 1:5 mM Ca2+:Mg2+. The maximum rate of substrate hydrolysis occurred a t pH 7.5-7.7, 37-45°C and with 3-5 mM ATP. Other triphosphate substrates were cleaved but ADP, AMP or p-nitrophenylphosphate were not, showing that the enzyme is a triphosphatase Mg2+ ATPase activity was not inhibited by ouabain or ruthenium red, and only slightly inhibited by ethacrynic acid, while La3+ had a slight stimulatory effect.