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首页> 外文期刊>International Journal of Molecular Sciences >Enzymatic Synthesis of Galactosylated Serine/Threonine Derivatives by β-Galactosidase from Escherichia coli
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Enzymatic Synthesis of Galactosylated Serine/Threonine Derivatives by β-Galactosidase from Escherichia coli

机译：大肠杆菌中β-半乳糖苷酶的酶促合成半乳糖基化丝氨酸/苏氨酸衍生物

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摘要

The transgalactosylations of serine/threonine derivatives were investigated using β-galactosidase from Escherichia coli as biocatalyst. Using ortho-nitrophenyl-β-d-galactoside as donor, the highest bioconversion yield of transgalactosylated N-carboxy benzyl l-serine benzyl ester (23.2%) was achieved in heptane:buffer medium (70:30), whereas with the lactose, the highest bioconversion yield (3.94%) was obtained in the buffer reaction system. The structures of most abundant galactosylated serine products were characterized by MS/MS. The molecular docking simulation revealed that the binding of serine/threonine derivatives to the enzyme’s active site was stronger (−4.6~−7.9 kcal/mol) than that of the natural acceptor, glucose, and mainly occurred through interactions with aromatic residues. For N-tert-butoxycarbonyl serine methyl ester (6.8%) and N-carboxybenzyl serine benzyl ester (3.4%), their binding affinities and the distances between their hydroxyl side chain and the 1′-OH group of galactose moiety were in good accordance with the quantified bioconversion yields. Despite its lower predicted bioconversion yield, the high experimental bioconversion yield obtained with N-carboxybenzyl serine methyl ester (23.2%) demonstrated the importance of the thermodynamically-driven nature of the transgalactosylation reaction.
机译：使用来自大肠杆菌的β-半乳糖苷酶作为生物催化剂，研究了丝氨酸/苏氨酸衍生物的反式半乳糖基化。使用邻硝基苯基-β-d-半乳糖苷作为供体，在庚烷：缓冲液（70:30）中，反式半乳糖基化的N-羧基苄基1-丝氨酸苄基酯的生物转化率最高（23.2％），而对于乳糖，在缓冲液反应系统中，生物转化率最高（3.94％）。 MS / MS表征了最丰富的半乳糖基化丝氨酸产物的结构。分子对接模拟显示，丝氨酸/苏氨酸衍生物与酶的活性位点的结合（-4.6〜-7.9 kcal / mol）比天然受体葡萄糖强（-4.6〜-7.9 kcal / mol），并且主要通过与芳香族残基的相互作用而发生。对于N-叔丁氧基羰基丝氨酸甲酯（6.8％）和N-羧基苄基丝氨酸苄基酯（3.4％），它们的结合亲和力以及它们的羟基侧链与半乳糖部分的1'-OH基团之间的距离均相符。定量的生物转化产量。尽管其较低的预测生物转化率，但使用N-羧基苄基丝氨酸甲酯（23.2％）获得的高实验生物转化率证明了转半乳糖基化反应的热力学驱动性质的重要性。

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