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Home page > Latest publications > Internal Water Dynamics Control the Transglycosylation/Hydrolysis Balance in the Agarase (AgaD) of Zobellia galactanivorans

Internal Water Dynamics Control the Transglycosylation/Hydrolysis Balance in the Agarase (AgaD) of Zobellia galactanivorans.
David, B., Irague, R., Jouanneau, D., Daligault, F., Czjzek, M., Sanejouand, Y.-H., & Tellier, C.
ACS Catalysis (2017), Volume 7, Pages 3357–3367

ABSTRACT

In retaining glycoside hydrolases (GHs), transglycosylase activity is often low due to the natural hydrolytic activity that is favored in water. Improving the relative transglycosylase activity of these enzymes is of particular interest to obtain enzymes suitable for the synthesis of oligosaccharides. We explored the effect of engineering the water dynamics within the endo-β-agarase AgaD on the transglycosylation/hydrolysis (T/H) balance. By mutating three amino acids (D341, Q342, and S351), which could control water access to a putative water channel ending close to the active site, we obtained AgaD variants with an inverted T/H balance. For the best mutant, D341L/Q342H/S351F, the hydrolysis activity was reduced 50-fold in comparison to the wild type, while the transglycosylase activity was maintained and even slightly improved. This variant produced a large amount of oligo-agaroses by a disproportionation reaction with deca-agarose as the substrate. Molecular dynamics simulations showed that these enzymatic modifications were correlated with higher water dynamics, as revealed by a marked reduction in the water survival time and a decrease in the purge time of water in a channel ending close to the active site. These results suggest that modifying the water dynamics in GHs could be a rational basis for engineering of transglycosylase activity.

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