Urinary excretion patterns of sialoglycoconjugates in patients with mucolipidosis

Excessive urinary excretion of sialoglycoconjugates was observed in 6 patients with mucolipidosis. Urinary sialoglycoconjugates were divided into 9 fractions by sequential gel filtration on Sephadex G-25 and G-50, and by Dowex 1 ion-exchange chromatography. In a comparative study on these fractions it was shown that the fractions rich in sialyl-oligosaccharide contents contributed to the increased urinary excretion of sialoglycoconjugates. The sialyl-oligosaccharides contained in these fractions possessed the core structure of the carbohydrate side chains of glycoproteins with an N-glycosidic linkage, and the sialyl residues in these oligosaccharides were linked to galactosyl residues by an α2,3- or α2,6-linkage. In contrast to the latter type oligosaccharides, the excretion levels of the former varied from patient to patient. The patients with ML II excreted the former oligosaccharide comparable to the excretion levels of the latter. In the patient with ML I the excretion levels of α2,3-linked oligosaccharide was far lower than those of α2,6-linked one, and the patients with macular cherry-red spots and myoclonus syndrome excreted only a trace amount of α2,3-linked oligosaccharide. Mechanisms of these different excretion patterns are discussed.