The chemical nature of the products obtained by the action of cabbage-leaf phospholipase D on lysolecithin: the structure of lysolecithin.

1. Lysolecithin, prepared by the action of snake-venom phospholipase A on ovolecithin, when incubated with Savoy-cabbage phospholipase D, in the presence of Ca(2+) ions, gave two degradation products (designated A and B) in the form of their calcium salts. 2. These calcium salts were separated quantitatively by solvent fractionation and converted into the corresponding sodium salts. 3. Substance B proved to be a lysophosphatidic acid of conventional structure (1-monoacyl-l-3-glycerophosphoric acid). When the phosphate group was removed by means of prostatic acid phosphomonoesterase, a 1-monoglyceride was formed quantitatively. Alkaline hydrolysis gave the theoretical yield of l-3-glycerophosphate. 4. Substance A, on the other hand, had all the properties expected for a cyclic phosphate of a 1-monoglyceride. It was unaffected by phosphomonoesterase. On alkaline hydrolysis, the acyl group was removed and ring opening of the presumed cyclic phosphate group gave an approximately equimolar mixture of 2- and l-3-glycerophosphates. 5. The structures of substances A and B confirm lysolecithin as 1-monoacyl-l-3-glycerylphosphorylcholine.