Sialidase/neuraminidase deficiency

There are other lysosomal disorders in addition to those shown in Figure 9.20 and Table 9.1. For instance, several types of fucosidoses exist, which affect such structures as glycoproteins and blood group substances. Sialidoses also exist. However, lysosomal fucosidase and sialidase (neuraminidase) deficiencies do not affect the degradation of gangliosides. 

In a patient classified as mucolipidosis I, Ckmzetal (1977) and Spranger /. (1977) demonstrated a severe deficiency of an acid neuraminidase (sialidase N-acetyl neuraminic acid hydrolase, E.C. 3.2.1.18) in his cultured fibroblasts. The patient had a neurodegenerative disorder with myoclonus, skeletal changes like in Hurler disease, and cherry-red spots in the maculae of his eyes. In addition to the neuraminidase defect, the fibroblasts of the patient accumulated abnormal amounts of sialic acid-containing compounds. The patient excreted excessive quantities of sialyloligosaccharides in the urine (Michalski etal 1977). Fibroblasts from the parents of another such patient had activities of neuraminidase which were intermediate between patients and controls (Cantz and... 

Deficient activity in lysosomal acid sialidase (a-neuraminidase) is the genetic defect underlying sialidosis. Sialic acid occurs at the nonreducing terminus of the carbohydrate chains of many glycoproteins and also as a characteristic component of gangliosides. However, there is no biochemical or enzymological... 

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