Sialyltransferases linkages synthesized

Since none of these enzymes have been extensively purified, they are differentiated from one another primarily by the nature of the acceptor and by the linkage synthesized. TTie general reaction catalyzed by the sialyl-transferases is shown in Fig. 9. Although at least four different sialic acids have been described (Gottschalk, 1960a), only two nucleotide sugar derivatives have been isolated, namely, CMP-2V-acetylneuraminic acid and CMP-N-glycolylneuraminic acid it is presently not known whether different enzymes catalyze the transfer of these two different N-acylneu-raminic acids and most of the sialyltransferase literature is limited to the more readily available CMP-N-acetylneuraminic acid. 

It thus appears that liver has at least two different sialyltransferases distinguished by the linkages synthesized and the amounts of these transferases can vary with both flie species and the stage of development of the liver (Hudgin and Schachta-, 1972). 

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