Substrate specificity, regiospecificity, and processivity in glycoside hydrolase family 74 - Archive ouverte HAL Access content directly
Journal Articles Journal of Biological Chemistry Year : 2019

Substrate specificity, regiospecificity, and processivity in glycoside hydrolase family 74

Abstract

Glycoside hydrolase family 74 (GH74) is a historically important family of endo-␤-glucanases. On the basis of early reports of detectable activity on cellulose and soluble cellulose derivatives, GH74 was originally considered to be a "cellulase" family, although more recent studies have generally indicated a high specificity toward the ubiquitous plant cell wall matrix glycan xyloglucan. Previous studies have indicated that GH74 xyloglu-canases differ in backbone cleavage regiospecificities and can adopt three distinct hydrolytic modes of action: exo, endo-dis-sociative, and endo-processive. To improve functional predictions within GH74, here we coupled in-depth biochemical characterization of 17 recombinant proteins with structural biology-based investigations in the context of a comprehensive molecular phylogeny, including all previously characterized family members. Elucidation of four new GH74 tertiary structures , as well as one distantly related dual seven-bladed ␤-propeller protein from a marine bacterium, highlighted key structure-function relationships along protein evolutionary trajectories. We could define five phylogenetic groups, which delineated the mode of action and the regiospecificity of GH74 members. At the extremes, a major group of enzymes diverged to hydrolyze the backbone of xyloglucan nonspecifically with a dissociative mode of action and relaxed backbone regiospecific-ity. In contrast, a sister group of GH74 enzymes has evolved a large hydrophobic platform comprising 10 subsites, which facilitates processivity. Overall, the findings of our study refine our understanding of catalysis in GH74, providing a framework for future experimentation as well as for bioinformatics predictions of sequences emerging from (meta)genomic studies.
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hal-02611195 , version 1 (18-05-2020)

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Grégory Arnal, Peter J Stogios, Jathavan Asohan, Mohamed Attia, Tatiana Skarina, et al.. Substrate specificity, regiospecificity, and processivity in glycoside hydrolase family 74. Journal of Biological Chemistry, 2019, 294 (36), pp.13233 - 13247. ⟨10.1074/jbc.RA119.009861⟩. ⟨hal-02611195⟩
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