Ochiai Hirofumi, Huang Wei, Wang Lai-Xi
Institute of Human Virology and Department of Biochemistry & Molecular Biology, University of Maryland School of Medicine, 725 West Lombard Street, Baltimore, MD 21201, United States.
Carbohydr Res. 2009 Mar 31;344(5):592-8. doi: 10.1016/j.carres.2009.01.016. Epub 2009 Jan 19.
An alternative synthesis of beta-Glcp-(1-->4)-GlcpNAc oxazoline is described, and its enzymatic reaction with the endo-beta-N-acetylglucosaminidase from Arthrobacter protophormiae (Endo-A) was re-investigated. Under normal transglycosylation conditions with a catalytic amount of enzyme, Endo-A showed only marginal activity for transglycosylation with the disaccharide oxazoline, consistent with our previous observations. However, when used in a relatively large quantity, Endo-A could promote the transglycosylation of the disaccharide oxazoline to a GlcpNAc-Asn acceptor. In addition to the initial transglycosylation product, a series of large oligosaccharides were also formed due to the tandem transglycosylation to the terminal glucose residues in the intermediate products. In the absence of an external acceptor, Endo-A could polymerize the disaccharide oxazoline to form oligo- and polysaccharides having the -4-beta-(Glcp-(1-->4)-beta -GlcpNAc)-1-repeating units. This is the first example of an endo-beta-N-acetylglucosaminidase-promoted polymerization of activated oligosaccharide substrates. This enzymatic polymerization may find useful applications for the synthesis of novel artificial polysaccharides.
描述了β-Glcp-(1→4)-GlcpNAc恶唑啉的另一种合成方法，并重新研究了其与来自原变形节杆菌的内切β-N-乙酰氨基葡萄糖苷酶（Endo-A）的酶促反应。在使用催化量酶的正常转糖基化条件下，Endo-A对二糖恶唑啉的转糖基化仅表现出微弱的活性，这与我们之前的观察结果一致。然而，当大量使用时，Endo-A可以促进二糖恶唑啉与GlcpNAc-Asn受体的转糖基化反应。除了初始的转糖基化产物外，由于对中间产物末端葡萄糖残基的串联转糖基化反应，还形成了一系列大的寡糖。在没有外部受体的情况下，Endo-A可以使二糖恶唑啉聚合形成具有-4-β-(Glcp-(1→4)-β-GlcpNAc)-1重复单元的寡糖和多糖。这是内切β-N-乙酰氨基葡萄糖苷酶促进活化寡糖底物聚合的首个实例。这种酶促聚合反应可能在新型人工多糖的合成中找到有用的应用。
