The X-ray crystal structure of an Arthrobacter protophormiae endo-beta-N-acetylglucosaminidase reveals a (beta/alpha)(8) catalytic domain, two ancillary domains and active site residues key for transglycosylation activity.

Glycoside hydrolase family GH85 is a family of endo-beta-N-acetylglucosaminidases that is responsible for the hydrolysis of beta-1,4 linkage in the N,N-diacetylchitobiose core of N-linked glycans. The endo-beta-N-acetylglucosaminidase from Arthrobacter protophormiae (Endo-A) is of particular interest, given its increasing use for the chemoenzymatic synthesis of bespoke N-glycans using N-glycan oxazolines as glycosyl donors. The E173Q variant of Endo-A is especially attractive for synthesis, as it is hydrolytically impaired but still able to catalyze N-glycan synthesis by transglycosylation using activated oxazoline donors.