Fat metabolism in higher plants: XIII. phosphatidic acid synthesis and diglyceride phosphokinase activity in mitochondria from peanut cotyledons*

Abstract

A phosphatidic acid is the major lipid to become labeled when Pi32 (inorganic orthophosphate labeled with P32), under conditions of oxidative phosphorylation, or ATP32 is fed to mito-choline and phosphatidylethanolamine in the mitochondria obtained a much higher level of P32, the only cofactor required was Mg++. The stimulation of phosphatidic acid synthesis by an α,β-diglyceride provided support for the view that this synthesis is due to diglyceride phosphokinase activity in the mitochondria. Evidence is also presented that this enzyme preparation is capable of phosphorylating α-monoglycerides with the formation of monoacyl phosphatidic acids. When Pi32 was added to slices of peanut cotyledons, the phosphatidyl-choline and phosphatidylethanolamine in the mitochondria obtained a much higher level of radioactivity than that observed in experiments with the isolated mitochondria.