Characterization of a Highly Selective 2″- O -Galactosyltransferase from Trollius chinensis and Structure-Guided Engineering for Improving UDP-Glucose Selectivity.

A novel 2″- O -galactosyltransferase TcOGT4 was discovered from Trollius chinensis . TcOGT4 could regio-specifically catalyze 2″- O -galactosylation of 17 flavone 8- C -β-d-glucosides and shows high preference for UDP-Gal. Molecular docking indicated that Pro361 may play a key role in sugar donor selectivity, and the P361W mutant exhibited significantly enhanced selectivity toward UDP-Glc. A total of 21 products including 17 new compounds were obtained, and 5 of them showed potent COX-2 inhibitory activities. TcOGT4 is the first reported 2″- O -galactosyltransferase for flavone C -glycosides, and could be a powerful biocatalyst to synthesize bioactive flavone glycosides.