Biochemistry of Polyglycerophosphatides. Effect of Divalent Cations on the Biosynthesis and Composition of Polyglycerophosphatides in Isolated Mitochondria
The effect of the addition of divalent cations on the formation of phosphatidylglycerophosphate, phosphatidylglycerol, and cardiolipin in isolated mitochondria from rat liver and guinea pig heart was studied. Although it was confirmed that the biosynthesis of phosphatidylglycerol in rat liver mitochondria does not require the addition of divalent cations, the addition of Mn2+ and Mg2+ has a profound effect on the level of synthesis and composition of polyglycerophosphatides. By developing a method for the preparation of membrane-bound labeled phosphatidylglycerol and an assay for the quantitative determination of polyglycerophosphatides, the high conversion of phosphatidylglycerol-2′-3H to cardiolipin-3H was established only in the presence of Mn2+ and/or Mg2+. Zn2+ and Ca2+, in the concentration tested, did not stimulate this conversion, nor were they inhibitory. In addition, the association of formed cardiolipin-3H with the mitochondrial membrane was demonstrated. Some implications of these findings are discussed.