Structural and Catalytic Functions of CatA

Hiraiwa summarized in his review the basic understanding of CatA biology [7]. A prominent role of CatA is the protection of lysosomal 15-galactosi-dase (P-gal) and neuraminidase 1 (Neu-1) from intralysosomal proteolysis by the formation of a multienzyme complex [8,9]. This complex is responsible for the breakdown of oligosaccharides attached to a variety of glycoproteins and glycolipids. 

CatA deficiency or mutations affecting the structural integrity of CatA, therefore, lead to accumulation of sialylated glycoconjugate substrates of Neu-1 and later to the severe genetic disease galactosialidosis [10]. Common clinical signs are massive edema, skeletal dysplasia, cherry red spots on the retina, and neurological deterioration. 

CatA knockout mice show a similar phenotype to human galactosialidosis patients and can be rescued by transplanting eiythroid precursor cells overexpressing human CatA [11]. 

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