The histopathological picture of Alzheimer’s disease is characterized by senile plaques and neurofibrillary tangles, and because the senile plaques form first, they are considered the initial lesion. Senile plaques are known to be formed by accumulation of β-amyloid peptide (Aβ). Aβ peptide is produced by the cleavage of amyloid precursor protein (APP) by two types of proteolytic enzymes. The first cleavage is performed by β-secretase (BACE1), and the second γ-secretase. It is thought that their inhibitors may be capable of serving as safe drugs for the treatment of Alzheimer’s disease. In recent years a glycosyltransferase involved in the biosynthesis of sugar chains (α2, 6-sialyltransferase) has also been shown to be cleaved by BACE1. The cleavage site was identified at the same time, and as a result it was demonstrated that in rats it produces cleavaged-type α2, 6-sialyltransferase (E41 Form). This product is purified antibody which can detect α2, 6-sialyltransferase (C-terminal).