Properties of the phospholipase D from peanut seeds

Abstract

1. 1. Phospholipase D hydrolyzed phosphatidyl glycerol in the absence of ether, but the rate of hydrolysis was accelerated considerably when ether was added. 2. 2. Although very dilute aqueous dispersions of lecithin (1 μM) or ultrasonically irradiated lecithin in water were hydrolyzed by the enzyme in the absence of ether, addition of ether enhanced phospholipase D activity. 3. 3. The enzyme cleaved the phospholipids bound to rat liver microsomes. Furthermore, microsomes favored the hydrolysis of aqueous dispersions of 0.8 mM lecithin in the absence of ether. 4. 4. The phospholipids associated with serum β-lipoproteins were not attacked by phospholipase D; moreover, β-lipoproteins inhibited the hydrolysis of dilute aqueous dispersions of lecithin (approx. 0.1 μM). 5. 5. Lecithin partitioned between ether and aqueous sodium acetate solutions, in the presence or absence of CaCl 2 (40 mM), at a ratio of 4 to 1. 6. 6. The hydrolysis of lecithin by phospholipase D in an ether-water system was shown to occur in the aqueous phase. 7. 7. Low concentrations (0.1–0.5 mM) of cetyltrimethylammonium bromide as well as the calcium salts of phosphatidic acid, phosphatidyl glycerol or phosphatidyl methanol activated the hydrolysis of lecithin in the biphasic ether-water system.