Immunoprecipitation and lectin blotting of β-site APP-cleaving enzyme 1 (BACE1), the N-glycosylated enzyme [112] responsible for the toxic β-secretase cleavage of APP [113], from the brains of AD patients revealed increased levels of bisecting GlcNAc, and crucially this increase was observed in both early and late stage patients [112]. Here, BACE1 is linked to Alzheimer disease.