Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
10870164 | FEBS Letters | 2014 | 7 Pages |
Abstract
Bacterial sialyltransferases of the glycosyltransferase family GT-80 exhibit pronounced hydrolase activity toward CMP-activated sialyl donor substrates. Using in situ proton NMR, we show that hydrolysis of CMP-Neu5Ac by Pasteurella dagmatis α2,3-sialyltransferase (PdST) occurs with axial-to-equatorial inversion of the configuration at the anomeric center to release the α-Neu5Ac product. We propose a catalytic reaction through a single displacement-like mechanism where water replaces the sugar substrate as a sialyl group acceptor. PdST variants having His284 in the active site replaced by Asn, Asp or Tyr showed up to 104-fold reduced activity, but catalyzed CMP-Neu5Ac hydrolysis with analogous inverting stereochemistry. The proposed catalytic role of His284 in the PdST hydrolase mechanism is to facilitate the departure of the CMP leaving group.
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Authors
Katharina Schmölzer, Christiane Luley-Goedl, Tibor Czabany, Doris Ribitsch, Helmut Schwab, Hansjörg Weber, Bernd Nidetzky,