Summerfield J A, Taylor M E
Biochim Biophys Acta. 1986 Sep 4;883(2):197-206. doi: 10.1016/0304-4165(86)90309-0.
Human serum contains lectins which inhibit the uptake of mannose- and N-acetylglucosamine-terminated glycoproteins by isolated rat hepatic sinusoidal cells. In these experiments, calcium-dependent and calcium-independent human serum mannose-binding proteins have been isolated by affinity chromatography using mannan linked to four different supports. In electroblots both calcium-dependent and -independent serum mannose-binding proteins bound radioiodinated mannan and invertase in the presence of calcium ions, but the binding of calcium-dependent serum mannose-binding proteins was abolished by EDTA. Chicken antibodies were raised against serum mannose-binding proteins and an ELISA was developed. The principal calcium-independent serum mannose-binding protein is mannose-specific IgG as judged by immunodiffusion and electroblotting with anti-human IgG antibodies. The calcium-dependent serum mannose-binding protein is probably the secreted form of an intracellular hepatocyte mannose-binding protein since: antibodies raised against the 30 kDa subunit of the calcium-dependent serum mannose-binding protein also bound 30 kDa subunits of whole liver homogenate and purified human liver mannose-binding protein; antibodies to the human liver mannose-binding protein bound to the 30 kDa subunit of the calcium-dependent serum mannose-binding protein; and the binding specificities of the calcium-dependent serum mannose-binding protein for N-acetylglucosamine and fucose as well as mannose, and its recognition of the core region of an oligosaccharide rather than only the peripheral sugars, were identical to those reported for the hepatocyte mannose-binding protein. The physiological ligands of these serum mannose-binding proteins are unknown but they could bind noxious glycoproteins which enter the circulation prior to their removal by the sinusoidal mannose receptor.
人血清中含有凝集素，可抑制分离的大鼠肝窦状细胞摄取甘露糖和N - 乙酰葡糖胺末端的糖蛋白。在这些实验中，通过使用与四种不同载体相连的甘露聚糖的亲和层析法，分离出了钙依赖性和非钙依赖性人血清甘露糖结合蛋白。在电印迹中，钙依赖性和非钙依赖性血清甘露糖结合蛋白在钙离子存在下均能结合放射性碘化甘露聚糖和转化酶，但EDTA可消除钙依赖性血清甘露糖结合蛋白的结合。制备了针对血清甘露糖结合蛋白的鸡抗体并开发了一种酶联免疫吸附测定法。通过免疫扩散和用抗人IgG抗体进行电印迹判断，主要的非钙依赖性血清甘露糖结合蛋白是甘露糖特异性IgG。钙依赖性血清甘露糖结合蛋白可能是细胞内肝细胞甘露糖结合蛋白的分泌形式，因为：针对钙依赖性血清甘露糖结合蛋白30 kDa亚基产生的抗体也能结合全肝匀浆和纯化的人肝甘露糖结合蛋白的30 kDa亚基；针对人肝甘露糖结合蛋白的抗体能与钙依赖性血清甘露糖结合蛋白的30 kDa亚基结合；并且钙依赖性血清甘露糖结合蛋白对N - 乙酰葡糖胺、岩藻糖以及甘露糖的结合特异性，及其对寡糖核心区域而非仅外周糖的识别，与报道的肝细胞甘露糖结合蛋白相同。这些血清甘露糖结合蛋白的生理配体尚不清楚，但它们可能结合有害的糖蛋白，这些糖蛋白在被窦状甘露糖受体清除之前进入循环。
