Phospholipase A2 activity of low density lipoprotein: evidence for an intrinsic phospholipase A2 activity of apoprotein B-100.
During oxidative modification of low density lipoprotein (LDL) there is extensive degradation of phosphatidylcholine (PtdCho) to lysophosphatidylcholine (lyso-PtdCho), with the removal of fatty acids from the 2 position. The phospholipase A2 (PLA2) activity responsible for hydrolysis is closely associated with LDL. By use of lipoxygenase-oxidized 2-[1-14C]linoleoyl PtdCho as the substrate and delipidated apoprotein B (apo-B), evidence is presented to show that (i) the activity is destroyed progressively during the oxidative modification of LDL; (ii) p-bromophenacyl bromide (pBPB), a histidine modifier that inhibits the oxidative modification of LDL, also substantially inhibits the PLA2 activity; and (iii) photooxidation of LDL in the presence of Rose Bengal completely inactivates the enzyme with concomitant loss of apo-B histidine residues. High molecular weight proteins from delipidated LDL, separated by polyacrylamide gel electrophoresis, showed PLA2 activity. It is suggested that apo-B itself may possess PLA2 activity.
Parthasarathy
S
S
Department of Medicine, University of California, San Diego, La Jolla 92093-0613.
Barnett
J
J
D000596:Amino Acids / Q000032:analysis; D053299:Apolipoprotein B-100; D001055:Apolipoproteins B / Q000097:blood*; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D007700:Kinetics; D008075:Lipoproteins, HDL / Q000097:blood / Q000302:isolation & purification; D008077:Lipoproteins, LDL / Q000097:blood* / Q000302:isolation & purification; D008244:Lysophosphatidylcholines; D010741:Phospholipases A / Q000097:blood*; D054467:Phospholipases A2; D013379:Substrate Specificity
D000596:Amino Acids; D053299:Apolipoprotein B-100; D001055:Apolipoproteins B; D008075:Lipoproteins, HDL; D008077:Lipoproteins, LDL; D008244:Lysophosphatidylcholines; D010741:Phospholipases A; D054467:Phospholipases A2