@article {4395,
	title = {UDP-N-trifluoroacetylglucosamine as an alternative substrate in N-acetylglucosaminyltransferase reactions},
	journal = {Carbohydrate Research},
	volume = {306},
	number = {1-2},
	year = {1998},
	note = {ISI Document Delivery No.: 100VZTimes Cited: 15Cited Reference Count: 28},
	month = {Jan},
	pages = {127-136},
	type = {Article},
	abstract = {The synthesis of UDP-N-trifluoroacetylglucosamine [uridine 5{\textquoteright}-(2-trifluoroacetamido-2-deoxy-alpha-D-glucopyranosyl diphosphate, UDP-GlcNAc-F-3] is reported. The compound is found to serve as a substrate for the {\textquoteright}core-2{\textquoteright} GlcNAc transferase (EC 2.4.1.102) that is involved in the biosynthesis, of O-linked glycoproteins and for the GlcNAcT-V transferase (EC 2.4. 1.155) that is a key biosynthetic enzyme controlling the branching pattern of cell surface complex Asn-linked oligosaccharides. The trisaccharide beta-o-Gal p-(1 {\textendash}> 3)-[beta-D-GlcpNAc-F-3(1 {\textendash}> 6)]alpha-D-GalpNAc-OR [R = (CH2)(8)CO2Me] was prepared from beta-D-Galp-(1 {\textendash}> 3)-alpha-D-GalpNAc-OR using the {\textquoteright}core-2{\textquoteright} GlcNAc transferase. The tetrasaccharide beta-D-GlcpNAc-(1 {\textendash}> 2)-[beta-D-GlcpNAc-F-3-(1 {\textendash}> 6)]-alpha-D-Manp-(1 {\textendash}> 6)-beta-D-Glcp-OR [R = (CH2)(7)CH3] was prepared from beta-D-GlcpNAc-(1 {\textendash}> 2)-alpha-D-Manp-(1 {\textendash}> 6)-beta-D-Glcp-OR [R = (CH2)(7)CH3] using the GlcNAcT-V transferase. Removal of the trifluoroacetyl group was achieved under mild basic conditions to give the corresponding glucosamine containing tetrasaccharide. These examples demonstrate the feasibility of introducing masked forms of glucosamine residues into oligosaccharides using GlcNAc-specific transferases. The requirement for the trifluoroacetamido group as a specific recognition element was evident in the observation that neither UDP-glucosamine nor UDP-glucose served as a donor substrates for the {\textquoteright}core-2{\textquoteright} GlcNAc transferase. (C) 1998 Elsevier Science Ltd. All rights reserved.},
	keywords = {GLYCOPROTEINS, N-acetylglucosaminyltransferase, OLIGOSACCHARIDE, OLIGOSACCHARIDES, ORGANIC-SYNTHESIS, RECOGNITION, SYNTHESIS, UDP-sugar analog},
	isbn = {0008-6215},
	url = {<Go to ISI>://000074837200012},
	author = {Sala, R. F. and MacKinnon, S. L. and Palcic, M. M. and Tanner, M. E.}
}
@article {7321,
	title = {BINDING-ENERGY AND CATALYSIS - FLUORINATED AND DEOXYGENATED GLYCOSIDES AS MECHANISTIC PROBES OF ESCHERICHIA-COLI (LACZ) BETA-GALACTOSIDASE},
	journal = {Biochemical Journal},
	volume = {286},
	year = {1992},
	note = {ISI Document Delivery No.: JN815Times Cited: 86Cited Reference Count: 40Part 3},
	month = {Sep},
	pages = {721-727},
	type = {Article},
	abstract = {Kinetic parameters for the hydrolysis of a series of deoxy and deoxyfluoro analogues of 2{\textquoteright},4{\textquoteright}-dinitrophenyl beta-D-galactopyranoside by Escherichia coli (lacZ) beta-galactosidase have been determined and rates found to be two to nine orders of magnitude lower than that for the parent compound. These large rate reductions result primarily from the loss of transition-state binding interactions due to the replacement of sugar hydroxy groups, and such interactions are estimated to contribute at least 16.7 kJ (4 kcal).mol-1 to binding at the 3, 4 and 6 positions and more than 33.5 kJ (8 kcal).mol-1 at the 2 position. The existence of a linear free-energy relationship between log(k(cat.)/K(m)) for these compounds and the logarithm of the first-order rate constant for their spontaneous hydrolysis demonstrates that electronic effects are also important and provides direct evidence for oxocarbonium ion character in the enzymic transition state. A covalent intermediate which turns over only extremely slowly (t1/2 = 45 h) accumulates during hydrolysis of the 2-deoxyfluorogalactoside, and kinetic parameters for its formation have been determined. This intermediate is nonetheless catalytically competent, since it re-activates much more rapidly in the presence of the transglycosylation acceptors methanol or glucose, thereby providing support for the notion of a covalent intermediate during hydrolysis of the parent substrates.},
	keywords = {ALPHA-D-GLUCOPYRANOSYL, D-GLUCOPYRANOSYL PHOSPHATES, ENZYME, GLYCOGEN-PHOSPHORYLASE, HYDROLYSIS, inhibitors, OLIGOSACCHARIDE, SITE, SPECIFICITY, SUBSTRATE},
	isbn = {0264-6021},
	url = {<Go to ISI>://A1992JN81500010},
	author = {McCarter, J. D. and Adam,Michael J. and Withers, S. G.}
}
