Galactosialidosis 3-galactosidase

Galactosialidosis is characterized by the simultaneous deficiencies of P-galactosidase and a-neuroaminidase. Clinical and pathological manifestations resemble those in GM1 gangliosidosis and like it show a range of severity. The underlying defect involves a protective protein, which stabilizes these two enzymes by a mechanism that is not understood. Curiously, the protective protein is itself a peptidase. The disorder is most common in Japan. The defective gene has been cloned and mutations have been identified. 

SASD must be discriminated from other disorders of sialic acid storage [3] (1) sialidosis and galactosialidosis, defects respectively in lysosomal sialidase and both sialidase and /1-galactosidase. (OMIM 256550 and 256540) (2) nonlysosomal sialuria (OMIM 269921). 

Table 4.3.6 Normal and pathological values of sialidase and f-galactosidase activity in cultured fibroblasts of controls and patients with sialidosis or galactosialidosis...

Not only the deficiency of a hydrolytic enzyme, but also of other proteins required for sphingolipid degradation can cause a sphingolipid storage disease. Besides deficiencies of activator proteins, this is the case in galactosialidosis. This disease is characterized by the secondary deficiency of P-galactosidase and sialidase activity. The primary defect is due to mutations within the protective protein, which forms a stable complex with the GMl-p-galactosidase and the lysosomal sialidase [47]. 

Galactosialidosis Similar to late-onset form of GMl gangliosidosis, with varying degrees of additional mucopolysaccharidosis-like features (Unknown) Protective protein (secondary defect in GMl ganglioside P-galactosidase and sialidase)... 

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