Cleaves the distal alpha 1,2-linked glucose residue from the Glc(3)Man(9)GlcNAc(2) oligosaccharide precursor. Required for the accumulation of seed storage proteins, the formation of protein bodies, cell differentiation, cellulose biosynthesis and organization (in cell walls), cell shape determination and organization (e.g. epidermal cells), and embryo development. Involved in root development. H2O + N(4)-(alpha-D-Glc-(1->2)-alpha-D-Glc-(1->3)-alpha-D-Glc-(1->3)-alpha-D-Man-(1->2)-alpha-D-Man-(1->2)-alpha-D-Man-(1->3)-[alpha-D-Man-(1->2)-alpha-D-Man-(1->3)-[alpha-D-Man-(1->2)-alpha-D-Man-(1->6)]-alpha-D-Man-(1->6)]-beta-D-Man-(1->4)-beta-D-GlcNAc-(1->4)-alpha-D-GlcNAc)-L-asparaginyl-[protein] = beta-D-glucose + N(4)-(alpha-D-Glc-(1->3)-alpha-D-Glc-(1->3)-alpha-D-Man-(1->2)-alpha-D-Man-(1->2)-alpha-D-Man-(1->3)-[alpha-D-Man-(1->2)-alpha-D-Man-(1->3)-[alpha-D-Man-(1->2)-alpha-D-Man-(1->6)]-alpha-D-Man-(1->6)]-beta-D-Man-(1->4)-beta-D-GlcNAc-(1->4)-alpha-D-GlcNAc)-L-asparaginyl-[protein] Glycan metabolism; N-glycan degradation. Constitutively expressed in roots, stems, leaves, flowers and siliques. Embryonic lethal. Impaired glucosidase activity leading to a strongly reduced cellulose content. Abnormal shrunken seeds with embryos arrested at the heart stage. Low levels of storage proteins in seeds accompanied by a loss of protein bodies, abnormal cell enlargement and occasional cell wall disruptions. Belongs to the glycosyl hydrolase 63 family.