Differential effect of lysophospholipids on activities of human plasma paraoxonase1, either soluble or lipid-bound |
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Authors: | Cheon Ho Park Su Duy Nguyen Mee Ree Kim Tae-Sook Jeong Dai-Eun Sok |
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Affiliation: | (1) Department of Food and Nutrition, Chungnam National University, Yuseong-Gu, 305-764 Daejon, Korea;(2) Lipid Metabolism Laboratory, Korea Research Institute of Bioscience and Biotechnology, 305-333 Daejon, Korea;(3) College of Pharmacy, Chungnam National University, 220 Gung-Dong, Yuseong-Gu, 305-764 Daejon, Korea |
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Abstract: | Interaction of paraoxonasel (PON1) with lysophospholipids was examined with respect to activity regulation and binding property.
Paraoxonase activity of purified PON1 was partially inhibited by palmitoyl-lysophosphatidylglycerol (palmitoyl-lysoPG) and
lysophosphatidylinositol (lysoPl), which had a stimulatory effect on arylesterase and diazoxonase activities. The selective
inhibition of paraoxonase activity by palmitoyl-lysoPG, characterized by noncompetitiveness and charge interaction, was also
observed with HDL-or dimyristoylphosphatidylcholine (DMPC)-bound PON1. Mean-while, lysophosphatidylcholine (lysoPC) stimulated
all three activities of purified PON1, although it stimulated DMPC-bound or HDL-bound PON1 to a lesser extent. The stimulatory
action of lysophospholipids was observed around their CMC, suggesting that micelle formation of lysophospholpids might be
involved in the stimulation of PON1 activity. Presumably in support of this, the tryptophan fluorescence intensity of PON1
was increased by lysophospholipids at concentrations required for the stimulation of PON1 activity. Separately, lysoPC stimulation
was less remarkable for DMPC-bound PON1 than for either dimyristoylphosphatidylserine (DMPS)-or dimyristoylphos-phatidylglycerol-bound
PON1, suggesting a tight association between PON1 and DMPC. In support of this, the stimulatory role of apolipoprotein A-I
was less prominent for DMPC-bound PON1 than for DMPS-bound PON1. Taken together, these data suggest that the inhibition of
paraoxonase activity by lysoPG or lysoPI may be due to binding to a site distinct from the active center, whereas the stimulation
by lysophospholipid may be ascribed to the micelle formation around the lipid-associable region of PON1. |
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