Endoglycosidase that releases N-glycans from glycoproteins by cleaving the beta-1,4-glycosidic bond in the N,N'-diacetylchitobiose core. Involved in the production of high-mannose type N-glycans during plant development and fruit maturation. Endohydrolysis of the N,N'-diacetylchitobiosyl unit in high-mannose glycopeptides and glycoproteins containing the -[Man(GlcNAc)2]Asn- structure. One N-acetyl-D-glucosamine residue remains attached to the protein, the rest of the oligosaccharide is released intact. Optimum pH is 6.0-7.0. No visible phenotype under normal growth conditions, but the double mutants engase85A and engase85B accumulate very high level of free N-glycans carrying two GlcNAc at the reducing end, but their counterparts with a single GlcNAc are completely absent. Belongs to the glycosyl hydrolase 85 family.