Neuraminidase Substrate Promiscuity Permits a Mutant <i>Micromonospora viridifaciens</i> Enzyme To Synthesize Artificial Carbohydrates
作者:Lydia L. Cheng、Fahimeh S. Shidmoossavee、Andrew J. Bennet
DOI:10.1021/bi500203p
日期:2014.6.24
hydrolysis reaction. These coupling efficiencies likely arise from nonselective interactions between the acceptor glycopyranoside and MvNA Y370G, which preferentially places a carbohydrate hydroxyl group rather than water in close proximity to the active site where this functionality intercepts the nascent neuraminyl oxacarbenium ion that is formed duringcleavage of the glycosidic bond in the aryl
在微小单孢菌神经氨酸酶(Mv NA)的活性位点将亲核氨基酸残基酪氨酸突变为小的非极性残基甘氨酸(Y370G )产生了一种从人工底物(即苯基N)转移N-乙酰神经氨酸的有效催化剂-乙酰基-β - d-神经氨酸)与糖受体(例如d-乳糖,d-葡萄糖,d-甘露糖,d-棉子糖,d-阿洛糖或d-果糖)形成N-乙酰基-α-神经氨酸耦合碳水化合物产品。此外,这种突变酶(MvNA Y370G)催化糖残基从人工底物2-氟苯基N-乙酰基-β - d-神经氨酸向甲基糖吡喃糖苷受体的转移。有趣的是,当在包含30%(v / v)乙腈的水溶液中进行转糖基化反应时,甲基吡喃葡萄糖苷和吡喃半乳糖苷的α-异头受体比其相应的β-异头异构体产生更高的产物收率。具体地,用2-氟苯基64小时的反应ñ -乙酰基β- d -neuraminide作为限制试剂和受体甲基α- d -galactopyranoside,甲基α- d吡喃葡萄糖苷,或甲基α-
3.BETA.-Hydroxysialic Acid Glycosides. I. Calcium-Binding Ability and Chemical and Enzymatic Stabilities.
Methyl alpha- and beta-glycosides of N-acetylneuraminic acid (Neu5Ac) and N-acetyl-3 beta-hydroxyneuraminic acid (Neu5Ac beta 3OH) (1-4) were prepared to evaluate their calcium-binding ability. (Methyl alpha-glucopyranosidonyl) alpha- and beta-, and 4-methylumbelliferyl alpha-glycosides of Neu5Ac and Neu5Ac beta 3OH (5-10) were also synthesized for the comparison of chemical and enzymatic stabilities