Cysteine Cathepsins in the secretory vesicle produce active peptides: Cathepsin L generates peptide neurotransmitters and cathepsin B produces beta-amyloid of Alzheimer's disease

► Cathepsin L in secretory vesicles participates in the biosynthesis of peptide neurotransmitters and hormones. ► Cathepsin B produces neurotoxic β-amyloid in secretory vesicles and represents a new drug target for Alzheimer's disease. ► The secretory vesicle proteome indicates the protein environment that supports cathepsins L and B in the production of active peptides. ► Cysteine cathepsins possess novel biological functions in secretory vesicles for health and disease.