Lipoprotein Nature of Red Cell Adenosine Triphosphatase

THE adenosine triphosphatase activity of stromata prepared from human red cells has recently been thoroughly investigated by Post et al. 1 and by Dunham and Glynn 2 . The authors were able to demonstrate that in this ATPase, which is activated by magnesium and shows optimal efficacy at p H 7, two fractions can be distinguished, one being activated by calcium and another being inhibited by calcium and activated by sodium and potassium. The part activated by sodium and potassium amounts to 30–50 per cent of the total, and is further characterized by being inhibited by cardiac glycosides. It thus shows striking similarity to the ATPase present in submicroscopic particles isolated from crab nerve sheaths as studied by Skou 3,4 . The dependence of these enzymes on sodium and potassium and their sensitivity towards cardiac glycosides strongly suggest that they play a part in the active transport of sodium and potassium through the cell membrane.