Pennington J E, Nussenzveig R H, Van Heusden M C
Department of Biochemistry, University of Arizona, Tucson 85721, USA.
J Lipid Res. 1996 May;37(5):1144-52.
Two insect lipoproteins, triacylglycerol-rich Aedes aegypti lipophorin and diacylglycerol-rich Manduca sexta lipophorin, were compared in their ability to load neutral lipid from fat body. When fat body of M. sexta was incubated in vitro with [3H]oleic acid, all radiolabeled fatty acids were esterified, predominantly to triacylglycerol. In A. aegypti fat body, however, half of the label remained as free fatty acids. When A. aegypti fat body was radiolabeled with [3H]glycerol, most of the radiolabel was incorporated in triacylglycerol. When either A. aegypti or M. sexta lipophorin was incubated with A. aegypti fat body, labeled with [3H]oleic acid, both lipophorins incorporated mainly radiolabeled free fatty acids, while almost no radiolabeled glycerides were transferred. When the same experiment was performed with A. aegypti fat body, radiolabeled with [3H]glycerol, very little transfer of radiolabeled glycerides was detected. In contrast, when either M. sexta or A. aegypti lipophorin was incubated with M. sexta fat body, both lipophorins incorporated neutral lipids, predominantly diacyglycerol. A. aegypti lipophorin incorporated half the amount of radiolabeled lipid, compared to M. sexta lipophorin. Lipophorins from both species were treated with triacylglycerol lipase of the yeast Candida cylindracea. Although this lipase readily delipidated M. sexta HDLp, it was not able to remove triacylglycerol from A. aegypti HDLp. The data presented suggest that, under the conditions used, lipid transfer from fat body to lipophorin in A. aegypti is not as efficient as in M. sexta.
对两种昆虫脂蛋白——富含三酰甘油的埃及伊蚊脂磷蛋白和富含二酰甘油的烟草天蛾脂磷蛋白从脂肪体装载中性脂质的能力进行了比较。当将烟草天蛾的脂肪体与[3H]油酸在体外孵育时，所有放射性标记的脂肪酸都被酯化，主要形成三酰甘油。然而，在埃及伊蚊的脂肪体中，一半的标记物仍以游离脂肪酸的形式存在。当用[3H]甘油对埃及伊蚊脂肪体进行放射性标记时，大部分放射性标记物被掺入三酰甘油中。当用[3H]油酸标记的埃及伊蚊脂肪体与埃及伊蚊或烟草天蛾的脂磷蛋白一起孵育时，两种脂磷蛋白主要掺入放射性标记的游离脂肪酸，而几乎没有放射性标记的甘油酯被转移。当对用[3H]甘油标记的埃及伊蚊脂肪体进行相同实验时，检测到放射性标记的甘油酯转移极少。相反，当用烟草天蛾或埃及伊蚊的脂磷蛋白与烟草天蛾的脂肪体一起孵育时，两种脂磷蛋白都掺入中性脂质，主要是二酰甘油。与烟草天蛾脂磷蛋白相比，埃及伊蚊脂磷蛋白掺入的放射性标记脂质量为其一半。两种昆虫的脂磷蛋白都用柱形假丝酵母的三酰甘油脂肪酶处理过。尽管这种脂肪酶能轻易地使烟草天蛾的高密度脂蛋白（HDLp）脱脂，但它无法从埃及伊蚊的HDLp中去除三酰甘油。所呈现的数据表明，在所使用的条件下，埃及伊蚊中从脂肪体到脂磷蛋白的脂质转移不如烟草天蛾高效。
