Diglyceride kinase and other path ways for phosphatidic acid synthesis in the erythrocyte membrane.

Abstract

Various pathways for the synthesis of phosphatidic acid in ghosts from human erythrocytes have been studied. The synthesis of phosphatidic acid by the diglyceride kinase reaction is 10–40 times more active than the synthesis of phosphatidic acid by phosphorylation of monoglyceride followed by acylation, and 2500 times more active than the synthesis by acylation of α-glycerophosphate. Diglyceride kinase activity is as great or greater than the Na+ + K+-dependent, ouabain-inhibitable, ATPase in the erythrocyte membrane; this is compatible with its being a component of the ATPase. Various factors influencing diglyceride kinase activity have been studied, such as detergents, the state of dispersion of the diglyceride substrate, freezing of the ghosts, Na+ and K+, and ouabain. The kinetic curve at 37° for phosphatidic acid synthesis from diglyceride shows an initial rapid component, followed after about 1 min by a slower component.