Ro le of phospholipids in the NA + ,K + -stimulated adenosine triphosphatase system of brain microsomes

Removal of phospholipids from brain microsomes using a purified, protease-free phospholipase C preparation led to proportional losses of net Na⁺,K⁺-stimulated adenosine triphosphatase, K⁺-stimulated p-nitrophenylphosphatase, and Na⁺-stimulated ADP-ATP exchange activities. These enzymatic activities were restored to 60–100% of control values by the addition of a variety of purified phospholipids, but not by detergents or EGTA. These findings support the concept of a general phospholipid requirement for this enzyme system. This work further suggests that phospholipids are important both for formation and decomposition of the phosphorylated intermediate (s) which probably participate in the net reaction.