Differential hydrolysis of molecular species of lipoprotein phosphatidylcholine by groups IIA, V and X secretory phospholipases A2.
Human groups IIA, V and X secretory phospholipases A2 (sPLA2s) were incubated with human HDL3, total HDL and LDL over a range of enzyme and substrate concentrations and exposure times. The residual phosphatidylcholines (PtdChos) were assayed by high performance liquid chromatography with electrospray ionization mass spectrometry (LC/ESI-MS). The enzymes varied markedly in their rates of hydrolysis of the different molecular species and in the production of lysoPtdCho. The sPLA2s were compared at a concentration of 1 microg/ml and an incubation time of 4 h, when all three enzymes showed significant activity. The groups V and X sPLA2 were up to 20 times more reactive than group IIA sPLA2. Group X sPLA2 hydrolyzed arachidonate and linoleate containing species preferentially, while group V hydrolyzed the linoleates in preference to polyunsaturates. In all instances, the arachidonoyl and linoleoyl palmitates were hydrolyzed in preference to the corresponding stearates by group X sPLA2. The group IIA enzyme appeared to hydrolyze randomly all diacyl molecular species. The minor alkylacyl and alkenylacyl glycerophosphocholines (GroPChos) were poor substrates for groups V and X sPLA2s and these phospholipids tended to accumulate. The present study demonstrates a preferential release of arachidonate from plasma lipoprotein PtdCho by group X sPLA2, as well as a relative resistance of polyunsaturated PtdChos to hydrolysis by group V enzyme, which had not been previously documented. The use of lipoprotein PtdCho as substrate with LC/ESI-MS identification of hydrolyzed molecular species eliminates much of the uncertainty about sPLA2 specificity arising from past analyses of fatty acid release from unknown or ill-defined sources.
Pruzanski
W
W
Inflammation Research Group, University of Toronto, Toronto, Canada.
Lambeau
L
L
Lazdunsky
M
M
Cho
W
W
Kopilov
J
J
Kuksis
A
A
D000818:Animals; D016466:CHO Cells; D006224:Cricetinae; D003412:Cricetulus; D054501:Group II Phospholipases A2; D054505:Group V Phospholipases A2; D054509:Group X Phospholipases A2; D006801:Humans; D006868:Hydrolysis; D007700:Kinetics; D008074:Lipoproteins / Q000378:metabolism*; D008075:Lipoproteins, HDL / Q000378:metabolism*; D008077:Lipoproteins, LDL / Q000378:metabolism*; D010713:Phosphatidylcholines / Q000378:metabolism*; D010741:Phospholipases A / Q000235:genetics / Q000502:physiology*; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D013379:Substrate Specificity
D008074:Lipoproteins; D008075:Lipoproteins, HDL; D008077:Lipoproteins, LDL; D010713:Phosphatidylcholines; D011994:Recombinant Proteins; D010741:Phospholipases A; D054501:Group II Phospholipases A2; D054505:Group V Phospholipases A2; D054509:Group X Phospholipases A2; C516365:PLA2G10 protein, human; C516299:PLA2G5 protein, human