Abnormal urinary excretion of sialoglycoconjugates in patients with mucolipidosis

Low molecular sialoglycoconjugates were isolated by the charcoal adsorption method from the urines of patients with mucolipidosis (one patient with mucolipidosis type I variant and three patients with mucolipidosis type II). The sialoglycoconjugates were fractionated into two major fractions (SG-1 and SG-2) by Sephadex G-25 gel filtration, and a strikingly increased excretion of the SG-1 fraction was observed in patients with these diseases. The SG-1 fraction from each type of mucolipidosis was fractionated into four subfractions by Sephadex G-50 gel filtration, and the fraction with the lowest molecular weight (SG-1-III) was found to contribute to the increase in the levels of SG-1. The SG-1-III fraction was further fractionated into 7 to 8 subfractions by ion-exchange chromatography. The comparison of the amounts and the chemical compositions of the subfractions suggested that the increase in SG-1 was dependent upon the increase in excretion of mannose-containing sialooligosaccharides with the structures closely related to the carbohydrate units of glycoproteins with an N-glycosidic linkage.