The pyroglutamate-modified amyloid-β peptides derived from Aβ40 (H-7422) and Aβ42 (H-4796) have gained considerable attention as potential key participants in the pathology of Alzheimer's disease (AD) due to their abundance in AD brain, high aggregation propensity, stability, and cellular toxicity. Aβ40 and 42 can be N-terminally truncated by action of cathepsin B. The cyclization of Glu³ is catalyzed by glutaminyl cyclase. Hence, inhibition of these enzymes could be a therapeutic approach to AD.