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- Title
Two N-terminally truncated variants of human β-galactoside α2,6 sialyltransferase I with distinct properties for in vitro protein glycosylation.
- Authors
Luley-Goedl, Christiane; Schmoelzer, Katharina; Thomann, Marco; Malik, Sebastian; Greif, Michael; Ribitsch, Doris; Jung, Christine; Sobek, Harald; Engel, Alfred; Mueller, Rainer; Schwab, Helmut; Nidetzky, Bernd
- Abstract
Sialic acid groups of protein N-glycans are important determinants of biological activity. Exposed at the end of the glycan chain, they are potential targets for glycan remodeling. Sialyltransferases (STs; EC 2.4.99) are the enzymes that catalyze the sialic acid transfer from a CMP-activated donor on to a carbohydrate acceptor in vivo. Recombinant expression of the full-length human β-galactoside α2,6 sialyltransferase I (ST6Gal-I) was hampered and therefore variants with truncated N-termini were investigated. We report on the distinct properties of two N-terminally truncated versions of ST6Gal-I, namely Δ89ST6Gal-I and Δ108ST6Gal-I, which were successfully expressed in human embryonic kidney cells. The different properties of these enzymes result most probably from the loss of interactions from helix α1 in the Δ108ST6Gal-I variant, which plays a role in acceptor substrate binding. The Km for N-acetyl-D-lactosamine was 10-fold increased for Δ108ST6Gal-I (84 mM) as compared to Δ89ST6Gal-I (8.3 mM). The two enzyme variants constitute a suitable tool box for the terminal modification of N-glycans. While the enzyme Δ89ST6Gal-I exhibited both ST (di-sialylation) and sialidase activity on a monoclonal antibody, the enzyme Δ108ST6Gal-I showed only ST activity with specificity for mono-sialylation.
- Subjects
GALACTOSIDES; SIALYLTRANSFERASES; GLYCOSYLATION; GLYCANS; SIALIC acids; CARBOHYDRATES; IN vitro studies
- Publication
Glycobiology, 2016, Vol 26, Issue 10, p1097
- ISSN
0959-6658
- Publication type
Article
- DOI
10.1093/glycob/cww046