The lysosomal carboxypeptidase A, Cathepsin A (CathA), is a serine protease with distinct functions. CathA protects sialidase Neu1 and β- galactosidase against proteolytic degradation by forming a multi-enzyme complex and was shown to be activating sialidase Neu1. Mutations in the CathA gene cause the lysosomal storage disease galactosialidosis. Patients with galactosialidosis are characterized with a broad range of clinical phenotypes, involving growth retardation, neurological deterioration and accumulation of vasoactive peptide, endothelin-1 in the brain. CathA is also a multi-catalytic enzyme with deamidase and esterase activity at neutral pH, and carboxypeptidase activity at acidic pH. Previous investigations have presented that CathA has specific enzyme activity against vasoactive and neuropeptides, including endothelin-1, oxytocin and substance P. A generated mouse model with inactive CathA enzyme activity (CathAS190A) showed significantly increased level of precursor endothelin-1 vasoactive peptide with increased arterial blood pressure. The aim of this study was to ascertain the regulatory role of CathA against other vasoactive peptide precursors such as oxytocin, endothelin-1 and substance P in vivo. In addition to the regulatory role of the enzyme, CathA’s involvement in learning ability, long term memory and motor cortex functioning was elucidated. Our results showed that CathA has a regulatory role on endothelin-1 and oxytocin peptides’ degradation, which is the reason of the increased accumulation in the brain hippocampus region for CathAS190A. Memory based Morris’ water maze and passive avoidance tests illustrated that CathAS190A animals had lower scores than control littermates, which let us to speculate that CathA may play significant role in memory consolidation and learning ability through its regulatory role on vasoactive peptide biology. Keywords: Cathepsin A, vasoactive, peptide, memory