SUBCELLULAR LOCALIZATION OF PHOSPHATIDYLINOSITOL SYNTHASE FROM GERMINATING SOYBEANS

CDP-1,2-diacyl-sn-glycerol: myo-inositol phosphatidyltransferase (EC. 2.7.8.11, phosphatidylinositol synthase) catalyzes the final step in the de novo synthesis of phosphatidylinositol. The subcellular localization of this enzyme from germinating soybeans was determined by differential centrifugation and sucrose gradient centrifugation. Differential centrifugation of the crude extract indicated that phosphatidylinositol synthase activity was primarily located in the fraction sedimenting between 12,000 ×g and 100,000 ×g. Sucrose gradient centrifugation of the crude extract indicated that phosphatidylinositol synthase was associated with the endoplasmic reticulum.