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Originally published In Press as doi:10.1194/jlr.M600161-JLR200 on September 27, 2006

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Journal of Lipid Research, Vol. 47, 2656-2667, December 2006
Copyright © 2006 by American Society for Biochemistry and Molecular Biology

The main triglyceride-lipase from the insect fat body is an active phospholipase A1: identification and characterization

Estela L. Arrese1, Rajesh T. Patel and Jose L. Soulages

Department of Biochemistry and Molecular Biology, Oklahoma State University, Stillwater, OK 74078

Published, JLR Papers in Press, September 27, 2006.

1 To whom correspondence should be addressed. e-mail: estela{at}biochem.okstate.edu

The main triglyceride-lipase (TG-lipase) from the fat body of Manduca sexta has been identified as the homolog of Drosophila melanogaster CG8552. This protein is conserved among insects and also shares significant sequence similarity with vertebrate phospholipases (PLs) from the phosphatidic acid preferring-phospholipase A1 (PA-PLA1) family. It is shown here that the TG-lipase is also a PL. TG-lipase and PL activities copurify and are inhibited by, or resistant to, the same lipase inhibitors, indicating that both activities are catalyzed by the same enzyme and active site. The PL activity of TG-lipase corresponded to PL type A1. The concentration dependence of lipase activity with TG and PL micellar substrates showed saturation kinetics, with apparent Km values of 152 ± 11 and 7.8 ± 1.1 µM, respectively. TG-lipase was able to hydrolyze the major phospholipid components of the lipid droplets, phosphatidylcholine and phosphatidylethanolamine. The enzyme hydrolyzes 77 molecules of TG for every molecule of PL contained in the lipid droplets. It was observed that the activation of lipolysis in vivo is accompanied by activation of the hydrolysis of phospholipids of the lipid droplets. These results suggest that the PL activity of the insect TG-lipase could be required to allow access of the lipase to TG molecules contained in the core of the lipid droplets.

Supplementary key words adipokinetic hormone • lipolysis • Manduca sexta


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