This mutation results in the loss of the C‐terminal region of the endopeptidase neprilysin (NEP) protein (OMIM #120520), which inactivates a broad spectrum of peptide substrates, such as enkephalins, neurokinin A, substance P, bradykinin, endothelin, somatostatin, and more others, including amyloid‐β (Aβ) protein, which accumulates in Alzheimer's disease (AD). The gene discussed is TAC1; the disease is Alzheimer disease.