出版社：American Society for Biochemistry and Molecular Biology
摘要：The main triglyceride-lipase (TG-lipase) from the fat body ofManduca sexta has been identified as the homolog of Drosophilamelanogaster CG8552. This protein is conserved among insectsand also shares significant sequence similarity with vertebratephospholipases (PLs) from the phosphatidic acid preferring-phospholipaseA1 (PA-PLA1) family. It is shown here that the TG-lipase isalso a PL. TG-lipase and PL activities copurify and are inhibitedby, or resistant to, the same lipase inhibitors, indicatingthat both activities are catalyzed by the same enzyme and activesite. The PL activity of TG-lipase corresponded to PL type A1.The concentration dependence of lipase activity with TG andPL micellar substrates showed saturation kinetics, with apparentKm values of 152 ± 11 and 7.8 ± 1.1 µM,respectively. TG-lipase was able to hydrolyze the major phospholipidcomponents of the lipid droplets, phosphatidylcholine and phosphatidylethanolamine.The enzyme hydrolyzes 77 molecules of TG for every moleculeof PL contained in the lipid droplets. It was observed thatthe activation of lipolysis in vivo is accompanied by activationof the hydrolysis of phospholipids of the lipid droplets. Theseresults suggest that the PL activity of the insect TG-lipasecould be required to allow access of the lipase to TG moleculescontained in the core of the lipid droplets.Supplementary key words adipokinetic hormone • lipolysis • Manduca sexta
