Expanded analyses of the functional correlations within structural classifications of glycoside hydrolases

Glycoside hydrolases (GHs) are greatly diverse in sequences and functions, but systematic studies of GH relationships based on structural information are lacking. Here, we report that GHs have multiple evolutionary origins and are structurally derived from 27 homologous superfamilies and 16 folds, but GHs are highly biased to distribute in a few superfamilies and folds. Six of these superfamilies are widely encoded by archaea, bacteria, and eukaryotes, indicating that they may be the most ancient in origin. Most superfamilies vary in enzyme function, and some, such as the superfamilies of (beta/alpha)(8)-barrel and (alpha/alpha)(6)-barrel structures, exhibit extreme functional diversity; this is highly positively correlated with sequence diversity. More than one-third of glycosidase activities show a phenomenon of convergent evolution, especially the degradation functions of GHs on polysaccharides. The GHs of most superfamilies have relatively narrow environmental distributions, normally with the highest abundance in hostassociated environments and a distribution preference for moderate low-temperature and acidic environments. Overall, our expanded analysis facilitates an understanding of complex GH sequence-struc ture-function relationships and may guide our screening and engineering of GHs. (C) 2021 The Authors. Published by Elsevier B.V. on behalf of Research Network of Computational and Structural Biotechnology.

Automated summary

Glycoside hydrolases (GHs) have multiple evolutionary origins and are structurally derived from 27 homologous superfamilies and 16 folds, with a bias towards a few superfamilies and folds. Different superfamilies exhibit variations in enzyme function, with some showing extreme functional diversity that is highly correlated with sequence diversity. Convergent evolution is observed in over one-third of glycosidase activities, especially in the degradation functions of GHs on polysaccharides.