N-glycosylation of proteins is initiated in the endoplasmic reticulum (ER) by the transfer of the preassembled oligosaccharide glucose-3-mannose-9-N-acetylglucosamine-2 from dolichyl pyrophosphate to acceptor sites on the target protein by an oligosaccharyltransferase complex. This core oligosaccharide is sequentially processed by several ER glycosidases and by an endomannosidase (E.C. 3.2.1.130), such as MANEA, in the Golgi. MANEA catalyzes the release of mono-, di-, and triglucosylmannose oligosaccharides by cleaving the alpha-1,2-mannosidic bond that links them to high-mannose glycans.