Arrese E L, Wells M A
Department of Biochemistry, University of Arizona, Tucson 85721-0088, USA.
J Lipid Res. 1997 Jan;38(1):68-76.
The pathway for the adipokinetic hormone-stimulated synthesis of sn-1,2-diacylglycerols in the adult Manduca sexta fat body was studied. Adult fat body lipids were labeled by feeding 5th instar larvae either with [9,10(n)-3H]oleic acid or [1(3)-3H] glycerol and after 32 days insects at the adult stage were used. This long-term prelabeling led to labeled fat body acylglycerols in which triacylglycerols comprised the main radioactive lipid component (95.5%), regardless of the radiolabeled compound used. Because the distribution of radioactivity among the lipid classes was very close to the mass distribution of the fat body lipid subspecies, it was concluded that homogeneous labeling of fat body lipids was obtained. After adipokinetic hormone treatment, an accumulation of radioactivity in the sn-1,2-diacylglycerol fraction was the only significant change found in the distribution of radioactivity among fat body lipids. The size of diacylglycerol pool increased 280% 60 min after adipokinetic hormone stimulation, whereas the fatty acid, monoacylglycerol and phosphatidic acid pool sizes remained constant. These results support the hypothesis that adipokinetic hormone-stimulated synthesis of sn-1,2-diacylglycerol in the fat body involves stereospecific hydrolysis of the triacylglycerol stores.
研究了成年烟草天蛾脂肪体中促脂肪动素刺激的sn-1,2-二酰基甘油合成途径。通过给五龄幼虫喂食[9,10(n)-3H]油酸或[1(3)-3H]甘油来标记成年脂肪体脂质，32天后使用处于成虫阶段的昆虫。这种长期预标记导致标记的脂肪体酰基甘油，其中三酰基甘油构成主要的放射性脂质成分（95.5%），无论使用哪种放射性标记化合物。由于脂质类别之间的放射性分布非常接近脂肪体脂质亚类的质量分布，因此得出结论，获得了脂肪体脂质的均匀标记。在促脂肪动素处理后，sn-1,2-二酰基甘油部分中放射性的积累是在脂肪体脂质中放射性分布中发现的唯一显著变化。促脂肪动素刺激60分钟后，二酰基甘油池的大小增加了280%，而脂肪酸、单酰基甘油和磷脂酸池的大小保持不变。这些结果支持了这样的假设，即促脂肪动素刺激脂肪体中sn-1,2-二酰基甘油的合成涉及三酰基甘油储存的立体特异性水解。
