This gene encodes a member of the peptidase S10 family of serine carboxypeptidases. Alternative splicing results in multiple transcript variants, at least one of which encodes a preproprotein that is proteolytically processed to generate two chains that comprise the heterodimeric active enzyme. This enzyme possesses deamidase, esterase and carboxypeptidase activities and acts as a scaffold in the lysosomal multienzyme complex. Mutations in this gene are associated with galactosialidosis. [provided by RefSeq, Nov 2015],catalytic activity:Release of a C-terminal amino acid with broad specificity.,disease:Defects in CTSA are the cause of galactosialidosis [MIM:256540]. It is an autosomal recessive disease.,function:Protective protein appears to be essential for both the activity of beta-galactosidase and neuraminidase, it associates with these enzymes and exerts a protective function necessary for their stability and activity. This protein is also a carboxypeptidase and can deamidate tachykinins.,similarity:Belongs to the peptidase S10 family.,subunit:Heterodimer of a 32 kDa chain and a 20 kDa chain; disulfide-linked.,