The Stale ~:)I*teXS~lrl' , IfZ*rchl (l-be .Vethcrlands3 ll{c~,-ivcd June 13th :c~2) SUMM \ NY An inve~tigation wa_~ made int~ the action of a human pancreatic phosph~lipase A on various synthetic ph~x~phatidcs. L-a-l)hosl)hatidyt ethanolamines were readily hydrolvsed in an aqueous system by this enzyme. Synthetic lecithin.,+, h,Jwever, were not attacked in an appreciable rate by the mammalian phospholipase A, contrary to the action J~f the enzymes from animal poisons. Addition of deoxycholate I or synthetic phosphatidic acid greatly enhanced the degradatiou of s~-nthetic lecithins by the pancreatic phospholipase A. The site of action of the human pancreatic phospholipase A was determined with the aid of mixed-acid lecithins and ph¢)sphatidyl ethanolamines containing it, different molecular positions combinati-ns of stearic and laurie acid, stearic and oleic acid, paknitic and linolentc aod, restw~ctively. Ihe enzyme was demonstrated to liberate always the fl-e:,~rified fatty acids while the ;e-attached fatty acid constituents were recovered in the pro;luted Iv~o cnrnpounds. Hence the mode of action of thi~ phospholipase A from hum;tn pancreas is identical to the action of the corresponding phnspholipase from animal poisons so far investigat-d. [NTI~ODUCTIOS Recently MAGEE et aL l purified pho.~pholipase A (ph~.~phatitle ac.vI-hydrolase, E.C. 3.1.I.4) from ]lUlnaFl pancreas. It js ur, kl]owtl which fatty acid t~¢ter bond of the ...... LIIg ldbl. phospholipid molecule is catalytically" hvdr.b,-m-d by this cu~vm,~. I Jr ,~., years phospholipase A from .snake venom (Crolahts adamantheus) has been demonstrated, contrary to earlier views, t~, act on the fl-~'ster position only ~-~. It cannot be. precluded that the mode of action of phospholipasc A from other biological origins might differ from the snake-venom enzyme b.v acting on v-ester or on both 7-and fl-ester positions of the phosphoglyceride molecule. For this reason a:~ h~vestigation was made on the site of action of the pancreatic paosphf~lipa.~: A, using ,,:ari<>us synthetic phospholipid suhstrates, containing within each molecule two different fatty acid constituents. * CoBt_rtbutio~ 1N'O. 3o in the series "'Metabolism and Functions of Phc~pha~des".

No abstract

The synthesis is described of two structurally isomeric L-a-lecithins containing as fatty acid residues butyric acid and oleic acid. Phospholipase A (EC 3.1.1.4) from Crotalus adamantcus hydrolysed the p-fatty acid linkage irrespective of the nature of the fatty acid constituent, though (y-oleoyl-/I-butyryl)-L-a-lecithin was found to be much more readily attacked than (y-butyryl-/?-oleoyl)-L-a-lecithin.