Cathepsin A also known as CTSA is a member of the peptidase S10 family of serine carboxypeptidases. Cathepsin A plays a crucial role in lysosomal function by forming a high molecular weight complex with β-galactosidase and α-neuraminidase, thereby protecting these enzymes from degradation within the lysosome. This protective mechanism is vital for maintaining cellular metabolism and ensuring proper peptide biosynthesis and protein degradation. Deficiencies in cathepsin A can lead to a cascade of issues, including the dysfunction of β-galactosidase and α-neuraminidase, which are essential for the breakdown of glycoproteins and glycolipids. The gene encoding human cathepsin A is located on chromosome 20q13.12, and mutations in this gene are associated with galactosialidosis, a lysosomal storage disorder characterized by the accumulation of undegraded substrates due to the deficiencies of these critical enzymes.