Biochemical basis of six different types of sialidosis

Presently, six different inborn diseases can be defined as siatidosis. The semiotogy of mucolipidsis Ii (LCell disease) is well known: the occurrence of numerous cytoplasmic i~clusions Ln cultured fibreblasts, the increase of the activ_:ty of several lysosomal hydrolases (except/3-#ucosidase and acid pP.osphatase) in extracellular fluids contrasting with a decrease of ",he same activities in cultured fibroblasts are the most significant elements of diagnosis [1--3] _ An elevated excre~'on of urinary sialyl-oligosaccharides has been obs~ "eed This defect of a-neuraminidase activity has been also found in cultured fibroblasts [7,8], but was not characteristic, in this case~ of a prima~ defect, since the other hydrolases were Mso defective. This primary defect in 0~-neuraminidase is in good agreement with many other observations which have been made en mucolipidosis tI such as an increase o~ electron~gativity of secreted hydrolases compared to intracellular or normal plasma hydrolases Recognition markets of secreted glycoproteins, including acidic hydrolases, have been identified for different types of tissues as galactose, N-acetylglucosamine or mannose [11]