Potential processive catalysis by an exo-hydrolase identified by experiment and computation

S4.4 Polysaccharide processing for biofuels
Location (hall): 
Start/end time: 
Tuesday, July 2, 2019 - 12:15 to 12:30

Laura Masgrau1

1Universitat Autònoma De Bracelona, Cerdanyola Del Vallès (Barcelona), Spain

In our group, we apply computational techniques (molecular modelling methods) to study different aspects of carbohydrates: from mechanistic aspects of the reactions catalysed by CAZy enzymes to recognition processes involving carbohydrates or their mimics. After some years studying the mechanism of retaining glycosyltransferases [1], more recently, we have also investigated the transglycosylation and hydrolysis reactions of a family GH1 β-glicosidase [2] and the product exit pathway of a plant exo β-glucosidases of family GH1 (HvExoI). This latter study, done in collaboration with Prof. M. Hrmova (University of Adelaide), has led us to suggest a potential processive mechanism for this polysaccharide hydrolysing enzyme thanks to the identification of a putative transient lateral cavity next to the -1/+1 subsites that would allow the exit of the hydrolyzed glucose product (Fig. 1). 

To the best of our kowledge, and contrary to the case of endoglucanases or cellobiohydrolases, this is a mechanism that has not been proposed for any exo-acting hydrolase. The finding could have implication for the biotechnological use of such enzymes (e.g. in biomass degradation).

Figure 1. Newly identified exit path for Glc product bound at -1 subsite of HvExoI.

  1. E.g: H. Gómez et al., J. Am. Chem. Soc., 2012, 134, 4743-52 & J. Am. Chem. Soc., 2013, 135, 7053-63; D. Albesa-Jové et al., Angew. Chem. Int. Ed., 2015, 54, 9898-9902; F. Mendoza et al., Org. Biomol. Chem., 2017, 15, 9095-9107.
  2. S. Romero-Téllez et al., under revision.
  3. V.A. Streltsov et al., under revision.