@article { ISI:000374224400004,
	title = {Mechanisms of the sialidase and trans-sialidase activities of bacterial sialyltransferases from glycosyltransferase family 80},
	journal = {GLYCOBIOLOGY},
	volume = {26},
	number = {4},
	year = {2016},
	month = {APR},
	pages = {353-359},
	abstract = {Many important biological functions are mediated by complex glycan structures containing the nine-carbon sugar sialic acid (Sia) at terminal, non-reducing positions. Sia are introduced onto glycan structures by enzymes known as sialyltransferases (STs). Bacterial STs from the glycosyltransferase family GT80 are a group of well-studied enzymes used for the synthesis of sialylated glycan structures. While highly efficient at sialyl transfer, these enzymes also demonstrate sialidase and trans-sialidase activities for which there is some debate surrounding the corresponding enzymatic mechanisms. Here we propose a mechanism for STs from the glycosyltransferase family GT80 in which sialidase and trans-sialidase activities occur through reverse sialylation of CMP. The resulting CMP-Sia is then enzymatically hydrolyzed or used as a donor in subsequent ST reactions resulting in sialidase and trans-sialidase activities, respectively. We provide evidence for this mechanism by demonstrating that CMP is required for sialidase and trans-sialidase activities and that its removal with phosphatase ablates activity. We also confirm the formation of CMP-Sia using a coupled enzyme assay. A clear understanding of the sialidase and trans-sialidase mechanisms for this class of enzymes allows for more effective use of these enzymes in the synthesis of glycoconjugates.},
	issn = {0959-6658},
	doi = {10.1093/glycob/cwv105},
	author = {Mehr, Kevin and Withers, Stephen G.}
}
