Chino H, Downer R G, Takahashi K
Biochim Biophys Acta. 1977 Jun 22;487(3):508-16. doi: 10.1016/0005-2760(77)90220-x.
A diacylglycerol-carrying lipoprotein was isolated from mature eggs of the silkworm, Philosamia cynthia and compared, for physiochemical properties, with the major diacylglycerol-carrying lipoprotein I (LP-I) of hemolymph. The two molecules are identical an electrophoretic mobility, structural configuration as revealed by electron microscopy, and amino acid composition. In addition mannose was detected in the lipid-free protein moiety, thus enabling classification of the molecules as glycoproteins. The molecules differ in lipid content with egg-LP-I containing only 3.6% of the diacylglycerol content of hemolymph LP-I and the phospholipid and cholesterol components also showing a marked reduction. Analysis of the LP-I and vitellogenin (another diacylglycerol-carrying lipoprotein; LP-II) concentrations of mature eggs indicates that the amounts of the two glycolipoproteins in eggs are insufficient to account for the total acylglycerol content of the eggs. The results suggest that LP-I functions as a true carrier-protein serving to transport diacylglycerol from the fat body to the ovary. This proposal is supported by the observation that LP-I isolated from the egg retains the physiological capacity of hemolymph-LPi to take up diacylglycerol from fat body. Thus it is suggested that LP-I is the major source of lipid for vitellogenesis, whereas vitellogenin is the primary source of protein.
从蓖麻蚕成熟卵中分离出一种携带二酰基甘油的脂蛋白，并将其理化性质与血淋巴中主要的携带二酰基甘油的脂蛋白I（LP-I）进行比较。这两种分子在电泳迁移率、电子显微镜显示的结构构型和氨基酸组成方面是相同的。此外，在无脂蛋白质部分检测到甘露糖，因此能够将这些分子归类为糖蛋白。这些分子的脂质含量不同，卵LP-I仅含血淋巴LP-I中二酰基甘油含量的3.6%，磷脂和胆固醇成分也显著减少。对成熟卵中LP-I和卵黄蛋白原（另一种携带二酰基甘油的脂蛋白；LP-II）浓度的分析表明，卵中这两种糖脂蛋白的量不足以解释卵中总酰基甘油的含量。结果表明，LP-I作为一种真正的载体蛋白，起到将二酰基甘油从脂肪体转运到卵巢的作用。从卵中分离出的LP-I保留了血淋巴LP-I从脂肪体摄取二酰基甘油的生理能力，这一观察结果支持了这一观点。因此，有人提出LP-I是卵黄发生的主要脂质来源，而卵黄蛋白原是蛋白质的主要来源。
