Polysialic Acid Synthesis on the <i>N</i> - and <i>O</i> -Glycans of Salmonid Polysialyltransferase ST8Sia IV

High Resolution Image Download MS PowerPoint Slide Extension of N - and O -glycans with linear sialic acid polymers (polySias) was described on a limited number of mammalian glycoproteins, including the α2,8-polysialyltransferases ST8Sia II and ST8Sia IV. Previous in vitro analyses have shown that ST8Sia IV from the salmonid fish Coregonus maraena ( Cma ) had high polysialylation activity and broader donor substrate specificity compared to its human counterpart. In this study, we investigated whether the fish ST8Sia IV was able to polysialylate N - and O -glycans of glycoproteins with a focus on its autopolysialylation capacity. Using a combination of strategies, including plant-based glycoengineering, we found that the Cma ST8Sia IV is able to use both types of acceptors for the formation of long polySia chains with a degree of polymerization of >40 consisting of N -acetylneuraminic acid and N -glycolylneuraminic acid. Given the importance of polySias in multiple health and disease states, the Cma ST8Sia IV represents a useful biocatalyst with applications in the fields of biosafe therapeutics and glycobiology.