Water extrusion in isolated subcellular fractions

Suspensions of phospholipids, prepared from rat-liver mitochondria or from soya bean, extrude water when serum albumin and a Mg²⁺-ethylenediaminetetraacetate complex is addes. None of many other chelators tested can replace ethylenediaminetetraacetate. The pH optimum is 7.1 for the soya-bean phosphatides and 8.5 for those prepared from mitochondira. Various characteristics of the reaction are similar to the one observed in dialysed rat-liver mitochondira, although in this latter system serum albumin is not required. While in the dialyzed-mitochondira system Ca²⁺ can be replaced by Mg²⁺, with the isolated phospholipid Mg²⁺ is unable to replace Ca². When dialyzed mitochondria are treate with proteolytic enzymes, the requirement for serum albumin is observed and one also finds that Mg²⁺ is now unable to replace Ca²⁺. Little decrease of water-extrusion reaction ibn dialyzed mitochondria occurs after neutral-lipid extraction, while a large decrease is seen after phospholipid removal.