The structure of the naturally occurring phosphoglycerides. 3. Action of moccasin-venom phospholipase A on ovolecithin and related substances

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Abstract
The enzymic degradation of ovolecithin and certain other phosphoglycerides in ethereal solution by snake-venom phospholipase A is stimulated by Ca2+ ions. The optimum Ca2+ ion concentration varies between 40 and 80 [mu][image], when the lecithin concentration varies between 1.3 and 3.3 m[image] The phospholipase A activity of moccasin venom is inhibited by ethylenediaminetetraacetic acid and by Zn2+ and Cu2+ ions, but not by iodoacetate or p-chloro-mercuribenzoate. All the natural and synthetic L-[alpha]-lecithins studied lost one ester group/molecule of substrate in the presence of the enzyme. Synthetic DL-[alpha]-lecithins lost only 0.5 mole of ester/molecule of substrate, whereas synthetic [beta]-lecithin did not undergo any enzymic hydrolysis. Egg phosphatidylethanolamine was degraded by phospholipase A when the ethereal solution was adjusted to pH 7. There is some evidence for the breakdown of phosphatidylserine and ethanolamine plasmalogen. Inositol phosphoglycerides were not attacked by moccasin-venom phospholipase A.