Yi D, Lee R T, Longo P, Boger E T, Lee Y C, Petri W A, Schnaar R L
Departments of Pharmacology and Neuroscience, The Johns Hopkins School of Medicine, 725 North Wolfe Street, Baltimore, MD 21205, USA, Department of Biology, The Johns Hopkins University, Baltimore, MD 21218, USA.
Glycobiology. 1998 Oct;8(10):1037-43. doi: 10.1093/glycob/8.10.1037.
Both the Entamoeba histolytica lectin, a virulence factor for the causative agent of amebiasis, and the mammalian hepatic lectin bind to N-acetylgalactosamine (GalNAc) and galactose (Gal) nonreducing termini on oligosaccharides, with preference for GalNAc. Polyvalent GalNAc-derivatized neoglycoproteins have >1000-fold enhanced binding affinity for both lectins (Adler,P., Wood,S.J., Lee,Y.C., Lee,R.T., Petri,W.A.,Jr. and Schnaar,R.L.,1995, J. Biol. Chem ., 270, 5164-5171). Substructural specificity studies revealed that the 3-OH and 4-OH groups of GalNAc were required for binding to both lectins, whereas only the E.histolytica lectin required the 6-OH group. Whereas GalNAc binds with 4-fold lower affinity to the E.histolytica lectin than to the mammalian hepatic lectin, galactosamine and N-benzoyl galactosamine bind with higher affinity to the E. histolytica lectin. Therefore, a synthetic scheme for converting polyamine carriers to poly-N-acyl galactosamine derivatives (linked through the galactosamine primary amino group) was developed to test whether such ligands would bind the E.histolytica lectin with high specificity and high affinity. Contrary to expectations, polyvalent derivatives including GalN6lys5, GalN4desmosine, GalN4StarburstTMdendrimer, and GalN8StarburstTMdendrimer demonstrated highly enhanced binding to the mammalian hepatic lectin but little or no enhancement of binding to the E.histolytica lectin. We propose that the mammalian hepatic lectin binds with greatest affinity to GalNAc "miniclusters," which mimic branched termini of N-linked oligosaccharides, whereas the E.histolytica lectin binds most effectively to "maxiclusters," which may mimic more widely spaced GalNAc residues on intestinal mucins.
溶组织内阿米巴凝集素是阿米巴病病原体的一种毒力因子，它与哺乳动物肝凝集素都能结合寡糖上的N-乙酰半乳糖胺（GalNAc）和半乳糖（Gal）非还原端，且更倾向于GalNAc。多价GalNAc衍生的新糖蛋白对这两种凝集素的结合亲和力增强了1000倍以上（阿德勒，P.，伍德，S.J.，李，Y.C.，李，R.T.，佩特里，W.A.，Jr.和施纳尔，R.L.，1995，《生物化学杂志》，270，5164 - 5171）。亚结构特异性研究表明，GalNAc的3-OH和4-OH基团是与这两种凝集素结合所必需的，而只有溶组织内阿米巴凝集素需要6-OH基团。虽然GalNAc与溶组织内阿米巴凝集素的结合亲和力比与哺乳动物肝凝集素低4倍，但半乳糖胺和N-苯甲酰半乳糖胺与溶组织内阿米巴凝集素的结合亲和力更高。因此，开发了一种将多胺载体转化为聚-N-酰基半乳糖胺衍生物（通过半乳糖胺伯氨基连接）的合成方案，以测试此类配体是否能以高特异性和高亲和力结合溶组织内阿米巴凝集素。与预期相反，包括GalN6lys5、GalN4去铁胺、GalN4星爆树状大分子和GalN8星爆树状大分子在内的多价衍生物对哺乳动物肝凝集素的结合能力显著增强，但对溶组织内阿米巴凝集素的结合增强很少或没有增强。我们提出，哺乳动物肝凝集素与GalNAc“微簇”结合亲和力最大，GalNAc“微簇”模拟N-连接寡糖的分支末端，而溶组织内阿米巴凝集素与“大簇”结合最有效，“大簇”可能模拟肠道粘蛋白上间隔更宽的GalNAc残基。
