Biochemical characterization of an α1,2-colitosyltransferase from<i>Escherichia coli</i>O55:H7
作者:Zhigang Wu、Guohui Zhao、Tiehai Li、Jingyao Qu、Wanyi Guan、Jiajia Wang、Cheng Ma、Xu Li、Wei Zhao、Peng G Wang、Lei Li
DOI:10.1093/glycob/cwv169
日期:2016.5
Colitose, also known as 3,6-dideoxy-l-galactose or 3-deoxy-l-fucose, is one of only five naturally occurring 3,6-dideoxyhexoses. Colitose was found in lipopolysaccharide of a number of infectious bacteria, including Escherichia coli O55 & O111 and Vibrio cholera O22 & O139. To date, no colitosyltransferase (ColT) has been characterized, probably due to the inaccessibility of the sugar donor, GDP-colitose. In this study, starting with chemically prepared colitose, 94.6 mg of GDP-colitose was prepared via a facile and efficient one-pot two-enzyme system involving an l-fucokinase/GDP-l-Fuc pyrophosphorylase and an inorganic pyrophosphatase (EcPpA). WbgN, a putative ColT from E. coli O55:H5 was then cloned, overexpressed, purified and biochemically characterized by using GDP-colitose as a sugar donor. Activity assay and structural identification of the synthetic product clearly demonstrated that wbgN encodes an α1,2-ColT. Biophysical study showed that WbgN does not require metal ion, and is highly active at pH 7.5–9.0. In addition, acceptor specificity study indicated that WbgN exclusively recognizes lacto-N-biose (Galβ1,3-GlcNAc). Most interestingly, it was found that WbgN exhibits similar activity toward GDP-l-Fuc (kcat/Km = 9.2 min−1 mM−1) as that toward GDP-colitose (kcat/Km = 12 min−1 mM−1). Finally, taking advantage of this, type 1 H-antigen was successfully synthesized in preparative scale.
Colitose,也称为 3,6-二脱氧-L-半乳糖或 3-脱氧-L-岩藻糖,是仅有的五种天然存在的 3,6-二脱氧己糖之一。在许多感染性细菌的脂多糖中发现了大肠糖,包括大肠杆菌 O55 和 O111 以及霍乱弧菌 O22 和 O139。迄今为止,尚未对大肠糖基转移酶 (ColT) 进行表征,这可能是由于糖供体 GDP-大肠糖难以获得。在本研究中,从化学制备的大肠糖开始,通过简便高效的一锅双酶系统制备了 94.6 毫克 GDP-大肠糖,该系统涉及 l-岩藻糖激酶/GDP-l-Fuc 焦磷酸化酶和无机焦磷酸酶 (EcPpA)。 WbgN(一种来自大肠杆菌 O55:H5 的假定 ColT)随后通过使用 GDP-colitose 作为糖供体进行克隆、过表达、纯化和生化表征。合成产物的活性测定和结构鉴定清楚地表明 wbgN 编码 α1,2-ColT。生物物理研究表明WbgN不需要金属离子,并且在pH 7.5-9.0时具有高活性。此外,受体特异性研究表明,WbgN 专门识别乳-N-二糖 (Galβ1,3-GlcNAc)。最有趣的是,我们发现 WbgN 对 GDP-l-Fuc (kcat/Km = 9.2 min−1 mM−1) 的活性与对 GDP-colitose (kcat/Km = 12 min−1 mM−1) 的活性相似。最后,利用这一点,成功地制备级合成了1型H抗原。