Sialic Acids

作者：Irving R. Johnston, Edward J. McGuire, Saul Roseman · 发表于：Journal of Biological Chemistry · 年份：1973 · 被引用次数：19 · 研究领域：Glycosylation and Glycoproteins Research、Enzyme Production and Characterization、Carbohydrate Chemistry and Synthesis

Abstract A procedure is described for the partial purification (up to 200-fold) of an N-acetylglucosaminyltransferase from goat colostrum. The enzyme catalyzes the transfer of N-acetylglucosamine from uridine diphosphate N-acetylglucosamine to glycoprotein acceptors containing terminal mannose residues. The most effective substrate was α1-acid glycoprotein (orosomucoid) from which terminal sialic acid, galactose, and N-acetylglucosamine residues were enzymatically removed. The transferase was inactive with a wide range of low molecular weight acceptors. It exhibited a broad pH optimum, between pH 6.1 and 8.2, required divalent cations for activity (Mn2+ being more effective than Mg2+), and gave Km values for UDP-N-acetylglucosamine and the modified orosomucoid of 0.8 mm and 2 to 4 mm, respectively. The enzyme was detected in a variety of rat tissues. The mode of action of the transferase and its relationship to the formation of glycoproteins are discussed.