Galactosialidosis sialidase

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)... 

The term sialidosis refers to a series of disorders, probably allelic, caused by genetic abnormalities in the lysosomal sialidase which removes the terminal sialic acids from carbohydrate chains of glycoproteins. The activity of the sialidase which cleaves the sialic acid moieties from some of the gangliosides, such as GM3 and polysialogangliosides, is not defective (see appropriate section in Scriver et al., 1995). Review of the earlier literature on sialidosis requires exceptional care. Some of the earlier cases reported as sialidosis may well have been cases of galactosialidosis, another distinct genetic disorder recognized much more recently (see below). 

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