However, alanyl aminopeptidase has limited activity against Ala-X sequences with acidic X residues [58], aminopeptidase and didpetidyl aminopeptidase activity is not significantly higher in soluble extracts of frontal cortex from AD brains [59], and overall Aβ production does not increase most in familial forms of AD or with age [40]. Here, CPQ is linked to Alzheimer disease.