@article {494,
	title = {Mechanistic aspects of enzymatic carbohydrate epimerization},
	journal = {Natural Product Reports},
	volume = {19},
	number = {3},
	year = {2002},
	note = {ISI Document Delivery No.: 566QLTimes Cited: 21Cited Reference Count: 214},
	month = {Jun},
	pages = {261-277},
	type = {Review},
	abstract = {Carbohydrate epimerases are enzymes that catalyze an inversion of stereochemistry at a stereogenic center in a sugar. This review focuses on the mechanistic strategies that are employed by this diverse family of enzymes, and is divided into the following sections: deprotonation/reprotonation, transient oxidation, cofactor independent, and mutarotation. The review is comprehensive up to Oct. 2001 and contains 216 references.},
	keywords = {2-EPIMERASE, ACETYLNEURAMINIC, ACID BIOSYNTHESIS, D-GLUCOSAMINE 2-EPIMERASE, D-MANNOHEPTOSE 6-EPIMERASE, GDP-L-FUCOSE, GLUCURONYL C-5 EPIMERASE, MANNURONAN C-5-EPIMERASE, N-ACETYLGLUCOSAMINE, RENIN-BINDING PROTEIN, SITE-DIRECTED MUTAGENESIS, UDP-GALACTOSE 4-EPIMERASE, VINELANDII},
	isbn = {0265-0568},
	url = {<Go to ISI>://000176439700001},
	author = {Samuel, J. and Tanner, M. E.}
}
@article {4074,
	title = {Eliminations in the reactions catalyzed by UDP-N-acetylglucosamine 2-epimerase},
	journal = {Journal of the American Chemical Society},
	volume = {119},
	number = {43},
	year = {1997},
	note = {ISI Document Delivery No.: YD815Times Cited: 33Cited Reference Count: 65},
	month = {Oct},
	pages = {10269-10277},
	type = {Article},
	abstract = {Mechanistic studies have been carried out on the bacterial enzyme UDP-N-acetylglucosamine 2-epimerase, which catalyzes the interconversion of UDP-N-acetylglucosamine (UDP-GlcNAc) and UDP-N-acetylmannosamine (UDP-ManNAc). This enzyme is interesting because it epimerizes a stereocenter that does not bear an acidic proton, and therefore it cannot utilize a simple deprotonation/reprotonation mechanism. A coupled enzyme assay employing UDP-ManNAc dehydrogenase has been developed. The epimerization in D2O is found to be accompanied by the incorporation of deuterium into the C-2 {\textquoteright}{\textquoteright} position of both epimers, supporting a mechanism that ultimately involves a proton transfer at this position. The epimerization of [2 {\textquoteright}{\textquoteright}-H-2]UDP-GlcNAc is slowed by a primary kinetic isotope effect indicating that C-H bond cleavage is occurring during a rate-determining step of the reaction. A positional isotope exchange (PM) experiment shows that an O-18 label in the sugar-UDP bridging position will scramble into nonbridging diphosphate positions during enzymatic epimerization. These observations are consistent with a mechanism that proceeds via cleavage of the anomeric C-O bond, with 2-acetamidoglucal and UDP as enzyme-bound intermediates. Additional evidence for this mechanism is found in the unusual observation that during extended incubations, the intermediates are gradually released from the enzyme and accumulate in solution. These intermediates are formed by an anti elimination of UDP from UDP-GlcNAc and a syn elimination of UDP from UDP-ManNAc. It is likely that El-like eliminations via oxocarbenium intermediates are involved in the reaction. Further experiments show that 3 {\textquoteright}{\textquoteright}-deoxy-UDP-GlcNAc is not a substrate for the enzyme and that the enzyme does not contain a tightly bound NAD(+) cofactor.},
	keywords = {BACILLUS-SUBTILIS, D-GLUCOSAMINE 2-EPIMERASE, enterobacterial common antigen, ESCHERICHIA-COLI, FATTY-ACID OXIDATION, GALACTOSE 4-EPIMERASE, POSITIONAL ISOTOPE EXCHANGE, RAT-LIVER, STAPHYLOCOCCUS-AUREUS-H, TEICHOIC-ACIDS, W23},
	isbn = {0002-7863},
	url = {<Go to ISI>://A1997YD81500003},
	author = {Morgan, P. M. and Sala, R. F. and Tanner, M. E.}
}
