I cell disease. A hypothesis for the structure of the carbohydrate recognition site on β-D-N-acetylhexosaminidase

I-cell disease (mucolipidosis II) is presented as a model for endo- and exo-cytosis phenomena in man. A hypothesis is presented for the structure of the carbohydrate recognition site on fibroblast-derived β-D-N-acetylhexosaminidase that may extend to the other affected hydrolases and that is responsible for specific uptake of the enzyme by fibroblasts. The proposed neuraminidase deficiency in I-cell disease is discussed in the light of its significance in influencing the final sugar sequence in the carbohydrate structure of the recognition site.