Lysophosphatidic acids are new substrates for the phosphatase domain of soluble epoxide hydrolase[S]
- Research Center for Environmental Bioscience and Department of Bioscience, School of Science and Technology, Kwansei Gakuin University, Sanda, Japan
Abstract
Soluble epoxide hydrolase (sEH) is a bifunctional enzyme that has a C-terminus epoxide hydrolase domain and an N-terminus phosphatase domain. The endogenous substrates of epoxide hydrolase are known to be epoxyeicosatrienoic acids, but the endogenous substrates of the phosphatase activity are not well understood. In this study, to explore the substrates of sEH, we investigated the inhibition of the phosphatase activity of sEH toward 4-methylumbelliferyl phosphate by using lecithin and its hydrolyzed products. Although lecithin itself did not inhibit the phosphatase activity, the hydrolyzed lecithin significantly inhibited it, suggesting that lysophospholipid or fatty acid can inhibit it. Next, we investigated the inhibition of phosphatase activity by lysophosphatidyl choline, palmitoyl lysophosphatidic acid, monopalmitoyl glycerol, and palmitic acid. Palmitoyl lysophosphatidic acid and fatty acid efficiently inhibited phosphatase activity, suggesting that lysophosphatidic acids (LPAs) are substrates for the phosphatase activity of sEH. As expected, palmitoyl, stearoyl, oleoyl, and arachidonoyl LPAs were efficiently dephosphorylated by sEH (Km, 3–7 μM; Vmax, 150–193 nmol/min/mg). These results suggest that LPAs are substrates of sEH, which may regulate physiological functions of cells via their metabolism.
Footnotes
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↵1 To whom correspondence should be addressed. e-mail: imaoka{at}kwansei.ac.jp
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- Abbreviations:
- EET
- epoxyeicosatrienoic acid
- GGPP
- geranylgeranyl pyrophosphate
- HAD
- haloacid dehalogenase
- LPA
- lysophosphatidic acid
- LPTC
- lysophosphatidyl choline
- 4-MUP
- 4-metylumbelliferyl phosphate
- PA
- phosphatidic acid
- PHO
- threo-9,10-phosphonooxyhydroxy-octadecanoic acid
- p-LPA
- palmitoyl lysophosphatidic acid
- S1P
- sphingosine-1-phosphate
- sEH
- soluble epoxide hydrolase
- s-LPA
- stearoyl lysophosphatidic acid
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This study was supported by the Project to Assist Private Universities in Developing Bases for Research of the Ministry of Education, Culture, Sports, Science and Technology of Japan and by the Japan Society for the promotion of Science Research Fellowship for young scientist.
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↵[S] The online version of this article (available at http://www.jlr.org) contains supplementary data in the form of two figures.
- Received November 4, 2011.
- Revision received December 30, 2011.
- Copyright © 2012 by the American Society for Biochemistry and Molecular Biology, Inc.
