Sialidase rans-Sialidases

While all these enzymes hydrolytically cleave a-glycosidic bonds of sialic acids, another type of sialidase has been discovered, which can also hydrolyze these linkages but preferably forms sialic acid linkages under physiological conditions in the presence of suitable acceptors. These are the /rans-sialidases, occurring in parasites, and a... 

Another system that couples glycohydrolase activity to glycosyltransferase activity has been reported. Ito and Paulson have developed a CMP-NeuAc recycling scheme that operates in conjunction with a tran -sialidase activity from Trypanosoma cruzi (Scheme 10) [34]. This trons-siaUdase catalyzes the reversible transfer of NeuAc from NeuAc(a2,3)Gal-OR to virtually any -linked galactoside substrate. The CMP-NeuAc recycling system is employed to circumvent the expense of the sialylated pentasaccharide donor substrate. Synthetically, NeuAc is first transferred to Gal(pi,3)-GlcNAc(pi,3)Gal(pi,4)Glc under catalysis by o2,3-SiaT. This pentasaccharide product is then a substrate for the /ran -sialidase. Several novel sialylated molecules were produced by this technique. 

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