The Sialic Acids
Year: 1973
Type: article
Abstract: A soluble sialyltransferase was partially purified from colostrum (goat, bovine, and human). This enzyme catalyzed the transfer of sialic acid from cytidine monophospho-sialic acid to β-d-galactopyranosides. When N-acetyllactosamine was the acceptor, the products formed by the colostrum transferase contained sialic acid linked only to C-6 of the galactose moiety; with lactose as the acceptor, a small fraction of the sialic acid was linked to C-3 as well. These results distinguish the colostrum enzyme from the previously reported rat mammary gland sialyltransferase, which synthesized only the C-3 isomers of sialyllactose and sialyl-N-acetyllactosamine. In addition, the colostrum enzyme exhibited the following important specificity requirements towards the acceptor: (a) high, rather than low molecular weight substrates were much more effective; (b) the penultimate sugar to which galactose was linked in disaccharides markedly influenced the kinetic parameters (Vmax and Km); and (c) the position of linkage of galactose to the penultimate sugar resulted in 40-fold changes in the rate of the reaction. The most active disaccharide was N-acetyllactosamine (4-O-β-d-galactopyranosyl-N-acetylglucosamine). This disaccharide is a structural component of many glycoproteins, and it is suggested that the colostrum sialyltransferase catalyzes the final step in the synthesis of the serum-type glycoproteins.
Source: Journal of Biological Chemistry
Institution: University of Michigan
Language: English
Subfield: Molecular Biology
Domain: Life Sciences
Open Access status: hybrid
Estimated APC paid: $3,430
OpenAlex ID: W1521754303