ABSTRACT
Phospholipase D is a hydrolytic enzyme which liberates the amino alcohol components from intact phospholipids. The base exchange enzymes catalyze the substitution of free ethanolamine, serine, and choline for a similar substitutent on the preexisting phospholipids. Dihexanoyl phosphatidylcholine was utilized as the substrate in the purification of the cabbage enzyme because it is a water-soluble lecithin analogue. The enzyme activity from rat brain microsomal membranes was solubilized and partially purified approximately 240-fold. The simplest function of this enzyme could be to remove “old” phospholipid molecules. However, this task is generally assigned to the enzyme repertoire of the “lysosomal” compartment of mammalian tissues. The base-exchange enzyme reactions are not responsible for net snythesis of any phospholipid, but rather for the remodeling of preexisting membrane phospholipids. Serine and ethanolamine base-exchange enzyme activities were copurified from solubilized rat brain membranes to a stage of apparent homogeniety based upon polyacrylamide gel electrophoresis.
