In contrast, in the epidermis of AD skin, as depicted in Figure 8, we thought it likely that the β-subunit would be generated both by auto-cleavage of the covalent peptide bond between Ile-142 in the α-subunit and Cys-143 in the β-subunit and by breaking the S-S bond (C31/C340) between the α- and β-subunits of aCDase via unknown mechanisms, which leads to the induction of SM deacylase activity. This evidence concerns the gene ASAH1 and Alzheimer disease.