[Galactosialidosis--protective protein and related enzymes]

Galactosialidosis is the inherited metabolic disease with autosomal recessive trait. This disease classifies into three classical subtypes and a variant type in clinically. In enzymatic assay, we observe the decreasing activities of both beta-galactosidase and neuraminidase, but now we know that the primarily cause of this disease is abnormality of protective protein. In 1988, the cDNA of human protective protein was cloned. From the cloning, the genetically abnormalities of this disease were detected and the difference of abnormalities about the proteins were studied between the clinical subtypes. Then, the abnormalities within the subtypes were confirmed the difference about the mature process of protective protein in expression study. The structure of this protein was shown in 1994-1995 and the abnormal mutated proteins were studied about stoichiometrical features. On the other hand, the functions of protective protein are identified to have the role of deamidase, esterase, and carboxypeptidase besides the protective function. In the galactosialidosis patients, these activities decrease in fact. We knew the reason of the difference within the subtypes of this disease using molecular biology methods at present. In the future, the model mouse will be prepared and we hope to produce the medicine for this disease.