Differential Biosynthesis of Polysialic Acid on Neural Cell Adhesion Molecule (NCAM) and Oligosaccharide Acceptors by Three Distinct α2,8-Sialyltransferases, ST8Sia IV (PST), ST8Sia II (STX), and ST8Sia III

• Published in: The Journal of biological chemistry Vol. 275; no. 24; pp. 18594 - 18601
• Main Authors: Angata, Kiyohiko, Suzuki, Misa, McAuliffe, Joseph, Ding, Yili, Hindsgaul, Ole, Fukuda, Minoru
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 16-06-2000
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M910204199

Polysialylated neural cell adhesion molecule (NCAM) is thought to play a critical role in neural development. Polysialylation of NCAM was shown to be achieved by two α2,8-polysialyltransferases, ST8Sia IV (PST) and ST8Sia II (STX), which are moderately related to another α2,8-sialyltransferase, ST8Sia III. Here we describe that all three α2,8-sialyltransferases can utilize oligosaccharides as acceptors but differ in the efficiency of adding polysialic acid on NCAM. First, we found that ST8Sia III can form polysialic acid on the enzyme itself (autopolysialylation) but not on NCAM. These discoveries prompted us to determine if ST8Sia IV and ST8Sia II share the property of ST8Sia III in utilizing low molecular weight oligosaccharides as acceptors. By using a newly established method, we found that ST8Sia IV, ST8Sia II, and ST8Sia III all add oligosialic and polysialic acid on various sialylatedN-acetyllactosaminyl oligosaccharides, including NCAMN-glycans, fetuin N-glycans, synthetic sialylated N-acetyllactosamines, and on α2-HS-glycoprotein. Our results also showed that monosialyl and disialyl N-acetyllactosamines can serve equally as an acceptor, suggesting that no initial addition of α2,8-sialic acid is necessary for the action of polysialyltransferases. Polysialylation of NCAM by ST8Sia IV and ST8Sia II is much more efficient than polysialylation of N-glycans isolated from NCAM. Moreover, ST8Sia IV and ST8Sia II catalyze polysialylation of NCAM much more efficiently than ST8Sia III. These results suggest that no specific acceptor recognition is involved in polysialylation of low molecular weight sialylated oligosaccharides, whereas the enzymes exhibit pronounced acceptor specificities if glycoproteins are used as acceptors.