Enzymatic synthesis of a 6'-sulphated sialyl-Lewisx which is an inhibitor of L-selectin binding to peripheral addressin.
Enzymatic synthesis of a 6'-sulphated sialyl-Lewisx which is an inhibitor of L-selectin binding to peripheral addressin.
复制标题
6-硫酸化唾液酸-Lewisx 的酶促合成，它是 L-选择素与外周地址素结合的抑制剂。
作者：
Peter R. Scudder;K. Shailubhai;Kevin L. Duffin;Philip R. Streeter;Gary S. Jacob
以前体二糖GlcNAc6OSO3β1-3Gal为原料，经过β-1，4-半乳糖基转移酶、α-2，3-反式唾液酸转移酶和重组α-1，3-岩藻糖基转移酶的一系列步骤，在酶的作用下合成了一种磺化形式的唾液酸路易斯X-NeuAcα2-3Galβ1-4(Fucα1-3)GlcNAc6OSO3β1-3Gal。在GlcNAc6OSO3残基的3位成功的酶促岩藻糖化反应表明，岩藻糖基转移酶能够在原位产生含有硫酸盐的硫化唾液酸路易斯X结构。该方法制备的磺化唾液酸路易斯X五糖抑制了可溶性L选择素与35SO4标记的外周地址蛋白的结合，IC50为0.8 mM，而唾液酸路易斯X四糖的抑制作用较弱，IC50为3.2 mM。Hemmerich和Rosen(BioChemical，33,4820-4829,1994)最近报道，除了6-O-半乳糖位置上的sialyl leisX结构外，小鼠外周地址蛋白Sgp50上还存在Galβ1-4GlcNAcO6SO3结构。根据我们的数据，我们认为6-O-GlcNAc位上的唾液酸路易斯X也可能存在于受体上，并作为L-选择素的配体发挥作用。
A sulphated form of sialyl-Lewisx, NeuAc alpha 2-3Gal beta 1-4(Fuc alpha 1-3)GlcNAc6OSO3 beta 1-3Gal, was synthesized enzymatically from a precursor disaccharide, GlcNAc6OSO3 beta 1-3Gal, using sequential steps involving beta 1,4-galactosyltransferase, alpha 2,3-trans-sialidase and recombinant alpha 1,3-fucosyltransferase, respectively. Successful enzymatic fucosylation at the 3 position of the GlcNAc6OSO3 residue demonstrated that fucosyltransferase are capable of generating, in situ, sulphated sialyl Lewisx structures containing sulphate at the 6 position of GlcNAc. The sulphated sialyl-Lewisx pentasaccharide produced by this procedure inhibited binding of a soluble form of L-selectin to 35SO4-labelled peripheral addressin with an IC50 of 0.8 mM, whereas sialyl-Lewisx tetrasaccharide was a weaker inhibitor, displaying an IC50 of 3.2 mM. Hemmerich and Rosen (Biochemistry, 33, 4820-4829, 1994) recently reported the presence of Gal beta 1-4GlcNAcO6SO3 structures on murine peripheral addressin Sgp50, in addition to sialyl Lewisx structures sulphated at the 6-O-galactose position. Based on our data, we suggest that sialyl Lewisx sulphated at the 6-O-GlcNAc position may also exist on receptors and function as a ligand for L-selectin.