Alteration of site-directed sugar chains of α_1-acid glycoprotein in serum of patients and its clinical significance

对正常人和炎症患者血清中α_1-酸性糖蛋白的N-糖链进行了比较研究(Clin Chim Acta，2003)。用唾液酸酶处理纯化的AGP，用MALDI-TOFMS分析其释放的N-糖链。两组N-糖链均由双、三、四触角组成，α-1-3岩藻糖基化N-糖链的含量为双-三-四触角。在炎症患者中，双触角增加，三触角和四触角减少，α1-3岩藻糖基化增加。纯化的AGP用Glu-C内切酶处理，并用MALDI-TOFMS测定用反相高效液相分离的各糖肽的N-糖链。每个糖基化位点由不同的和特有的触角多聚糖组成，在1和2位点由双和三个触角组成，在3到5位由三个和四个触角组成。在炎症性，I…在所有的糖基化位点中，双触角的增加、三触角和四触角的减少以及α_1-3岩藻糖基化的增加是常见的，急性炎症的程度大于慢性炎症。为了确定N-糖链的癌变，我们研究了人肝癌细胞株HuH7和HepG2分泌的糖蛋白的N-糖链。在α细胞分泌的几种糖蛋白中，三触角、四触角和Hep 1-3岩藻糖基化显著增加。此外，α1-3对NeuAcα2-3GalGalβ1-4GlcNAc-R的活性比HuH7高20倍。为了阐明高岩藻糖化N-糖链的生物学作用，将NK细胞放在包被高岩藻糖化糖蛋白的平板上进行刺激(未发表结果)。高岩藻糖化的糖蛋白将调节NK细胞的功能，因为17 kDa的蛋白被刺激在其酪氨酸残基上磷酸化。进一步的研究正在进行中。较少

N-Glycans of α_1-acid glycoprotein (AGP) in sera of healthy individuals and patients with inflammation were comparatively studied (Clin Chim Acta, 2003). N-Glycans released from purified AGP with N-glycanase were treated with sialidase and subjected to MALDI-TOFMS analysis. N-Glycans of both groups were composed with bi-, tri-and tetra-antennary complex-types and the contents of α1-3 fucosylated N-glycans were bi-□tri-<tetra-antennary. In inflammation patients, increases in bi-antennary, decreases in tri-and tetra-antennary and increases in α1-3 fucosylation were significant.N-Glycans of 5 glycosylation sites in AGP were separately compared (in preparation). Purified AGP was treated with endopeptidase Glu-C and N-glycans of each glycopeptides isolated by a reversed phase HPLC were determined by MALDI-TOFMS. Each glycosylation site was composed with different and characteristic antennary glycans, bi-and tri-in sites 1 and 2 and tri-and tetra-antennary in sites 3 to 5. In inflammatory, i … More ncreases in bi-antennary, decreases in tri-and tetra-antennary and increases in α_1-3 fucosylation were commonly observed in all glycosylation sites, in larger degrees in acute than chronic inflammation.To determine cancerous alteration of N-glycans, N-glycans of glycoproteins secreted from human hepatoma cell lines HuH7 and HepG2 were studied (Anal Sci, 2003). Increases in tri-and tetra-antennary and α1-3 fucosylation were prominently detected in several glycoproteins secreted by HepG2 cells. Moreover, α1-3 fucosylation activities toward NeuAcα2-3Galβ1-4GlcNAc-R were detected 20-fold highly in HepG2, comparing to HuH7.To clarify the biological roles of high-fucosylated N-glycans, NK cells were stimulated on plates coated with high-fucosylated glycoproteins purified from HepG2 culture, medium (unpublished result). High-fucosylated glycoproteins will modulate the NK cell functions, since protein with 17kDa was stimulated to phosphorylate on its tyrosine residues. Further study is in progress. Less