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BIOCHEMICAL PROCESSES AND MACROMOLECULAR STRUCTURES

At4g24160, a Soluble Acyl-Coenzyme A-Dependent Lysophosphatidic Acid Acyltransferase^1,[W],[OA]

Department of Biochemistry, Indian Institute of Science, Bangalore 560012, India (A.K.G., N.C., R.R.); Institute of Biochemistry, Graz University of Technology, A–8010 Graz, Austria (S.R., G.D.); and School of Science, Monash University, 46150 Petaling Jaya, Malaysia (R.R.)

Human CGI-58 (for comparative gene identification-58) and YLR099c, encoding Ict1p in Saccharomyces cerevisiae, have recently been identified as acyl-CoA-dependent lysophosphatidic acid acyltransferases. Sequence database searches for CGI-58 like proteins in Arabidopsis (Arabidopsis thaliana) revealed 24 proteins with At4g24160, a member of the /β-hydrolase family of proteins being the closest homolog. At4g24160 contains three motifs that are conserved across the plant species: a GXSXG lipase motif, a HX₄D acyltransferase motif, and V(X)₃HGF, a probable lipid binding motif. Dendrogram analysis of yeast ICT1, CGI-58, and At4g24160 placed these three polypeptides in the same group. Here, we describe and characterize At4g24160 as, to our knowledge, the first soluble lysophosphatidic acid acyltransferase in plants. A lipidomics approach revealed that At4g24160 has additional triacylglycerol lipase and phosphatidylcholine hydrolyzing enzymatic activities. These data establish At4g24160, a protein with a previously unknown function, as an enzyme that might play a pivotal role in maintaining the lipid homeostasis in plants by regulating both phospholipid and neutral lipid levels.

The author responsible for distribution of materials integral to the findings presented in this article in accordance with the policy described in the Instructions for Authors (www.plantphysiol.org) is: Ram Rajasekharan (lipid{at}biochem.iisc.ernet.in).

^[W] The online version of this article contains Web-only data.

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www.plantphysiol.org/cgi/doi/10.1104/pp.109.144261

^* Corresponding author; e-mail lipid{at}biochem.iisc.ernet.in.

Received July 3, 2009; accepted August 17, 2009; published August 21, 2009.