Padi2, encoding protein-arginine deiminase type-2 (PADI2) that converts arginine residues in proteins into citrullines (citrullination) through deamination [75], and Ide, encoding a ubiquitously expressed metalloprotease (IDE) that cleaves peptides including Aβ [76, 77], are noteworthy because their expression is upregulated in postmortem AD patient brains compared with age-matched controls. Here, IDE is linked to Alzheimer disease.