Mechanism of cooperative N-glycan processing by the multi-modular endoglycosidase EndoE

EndoE is a multi-domain glycoside hydrolase of the human pathogen Enterococcus faecalis. Here, the authors present crystal structures of EndoE and provide biochemical insights into the molecular basis of EndoE's substrate specificity and catalytic mechanism. Bacteria produce a remarkably diverse range of glycoside hydrolases to metabolize glycans from the environment as a primary source of nutrients, and to promote the colonization and infection of a host. Here we focus on EndoE, a multi-modular glycoside hydrolase secreted by Enterococcus faecalis, one of the leading causes of healthcare-associated infections. We provide X-ray crystal structures of EndoE, which show an architecture composed of four domains, including GH18 and GH20 glycoside hydrolases connected by two consecutive three alpha-helical bundles. We determine that the GH20 domain is an exo-beta-1,2-N-acetylglucosaminidase, whereas the GH18 domain is an endo-beta-1,4-N-acetylglucosaminidase that exclusively processes the central core of complex-type or high-mannose-type N-glycans. Both glycoside hydrolase domains act in a concerted manner to process diverse N-glycans on glycoproteins, including therapeutic IgG antibodies. EndoE combines two enzyme domains with distinct functions and glycan specificities to play a dual role in glycan metabolism and immune evasion.

Automated summary

This study presents the crystal structures of the multi-domain glycoside hydrolase EndoE from the human pathogen Enterococcus faecalis and provides insights into its substrate specificity and catalytic mechanism. EndoE combines two enzyme domains with distinct functions and glycan specificities to play a dual role in glycan metabolism and immune evasion.