A cell-free particulate system capable of effecting oxidative phosphorylation has been prepared from unfertilized eggs of Arbacia punctulata. A substantial increase in phosphorylation can be produced by addition of alpha-ketoglutarate, oxalacetate, or succinate, the magnitude of the increase being greatest with alpha-ketoglutarate. The activity of the phosphorylating system is sharply dependent on maintenance of a comparatively narrow pH range during both the preparation of the particulate system and its subsequent incubation with oxidizable substrate. 2. The maximum oxygen consumption of the cell-free particulate system derived from a given weight of unfertilized eggs is about three times that of the same weight of intact unfertilized eggs and approximately the same as that of an equal weight of fertilized eggs. 3. The data indicate that generation of high-energy phosphate bonds in the Arbacia egg is coupled, as it is in mammalian liver or kidney, with the functioning of the tricarboxylic acid cycle.
