15839-70-0Relevant articles and documents
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Ginsburg
, p. 4426 (1958)
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Biochemical characterization of an α1,2-colitosyltransferase from Escherichia coli O55:H7
Wu, Zhigang,Zhao, Guohui,Li, Tiehai,Qu, Jingyao,Guan, Wanyi,Wang, Jiajia,Ma, Cheng,Li, Xu,Zhao, Wei,Wang, Peng G.,Li, Lei
, p. 493 - 500 (2016)
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.
A High-Throughput Glycosyltransferase Inhibition Assay for Identifying Molecules Targeting Fucosylation in Cancer Cell-Surface Modification
Zhang, Xiaohua,Chen, Fei,Petrella, Alessandro,Chacón-Huete, Franklin,Covone, Jason,Tsai, Teng-Wei,Yu, Ching-Ching,Forgione, Pat,Kwan, David H.
, p. 715 - 724 (2019/03/26)
In cancers, increased fucosylation (attachment of fucose sugar residues) on cell-surface glycans, resulting from the abnormal upregulation of the expression of specific fucosyltransferase enzymes (FUTs), is one of the most important types of glycan modifications associated with malignancy. Fucosylated glycans on cell surfaces are involved in a multitude of cellular interactions and signal regulation in normal biological processes, as well as in disease. For example, sialyl LewisX is a fucosylated cell-surface glycan that is abnormally abundant in some cancers where it has been implicated in facilitating metastasis, allowing circulating tumor cells to bind to the epithelial tissue within blood vessels and invade into secondary sites by taking advantage of glycan-mediated interactions. To identify inhibitors of FUT enzymes as potential cancer therapeutics, we have developed a novel high-throughput assay that makes use of a fluorogenically labeled oligosaccharide as a probe of fucosylation. This probe, which consists of a 4-methylumbelliferyl glycoside, is recognized and hydrolyzed by specific glycoside hydrolase enzymes to release fluorescent 4-methylumbelliferone, yet when the probe is fucosylated prior to treatment with the glycoside hydrolases, hydrolysis does not occur and no fluorescent signal is produced. We have demonstrated that this assay can be used to measure the inhibition of FUT enzymes by small molecules, because blocking fucosylation will allow glycosidase-catalyzed hydrolysis of the labeled oligosaccharide to produce a fluorescent signal. Employing this assay, we have screened a focused library of small molecules for inhibitors of a human FUT enzyme involved in the synthesis of sialyl LewisX and demonstrated that our approach can be used to identify potent FUT inhibitors from compound libraries in microtiter plate format.
Mechanism and active site residues of GDP-fucose synthase
Lau, Stephen T. B.,Tanner, Martin E.
experimental part, p. 17593 - 17602 (2009/07/19)
L-Fucose, 6-deoxy-L-galactose, is a key component of many important glycoconjugates including the blood group antigens and the Lewisx ligands. The biosynthesis of GDP-L-fucose begins with the action cof a dehydratase that converts GDP-D-mannose into GDP-4-keto-6-deoxy-mannose. The enzyme GDP-fucose synthase, GFS, (also known as GDP-4-keto-6-deoxy-D-mannose epimerase/reductase, GMER) then converts GDP-4-keto-6-deoxy-D-mannose into GDP-L-fucose. The GFS reaction involves epimerizations at both C-3 and C-5 followed by an NADPH-dependent reduction of the carbonyl at C-4. This manuscript describes studies that elucidate the order of the epimerization steps and the roles of the active site acid/base residues responsible for the epimerizations. An active site mutant, Cys109Ser, produces GDP-6-deoxy-D-altrose as its major product indicating that C-3 epimerization occurs first and premature reduction of the GDP-4-keto-6-deoxy-D-altrose intermediate becomes competitive with GDP-L-fucose production. The same mutation results in the appearance of a kinetic isotope effect when [3 - 2H]-GDP-6-deoxy-4-keto- mannose is used as a substrate. This indicates that Cys109 is the base responsible for the deprotonation of the substrate at C-3. The Cys109Ser mutant also catalyzes a rapid wash-in of solvent derived deuterium into the C-5 position of GDP-fucose in the presence of NADP+. This confirms the order of epimerizations and the role of Cys109. Finally, the inactive His179Gln mutant readily catalyzes the wash-out of deuterium from the C-3 position of [3 - 2H]-GDP-6- deoxy-4-keto-mannose. Together these results strongly implicate an ordered sequence of epimerizations (C-3 followed by C-5 ) and suggest that Cys109 acts as a base and His179 acts as an acid in both epimerization steps.
