I-cell disease (also identified as mucolipidosis type II) is characterized by the presence of inclusion bodies in fibroblasts (hence the derivation of the term I-cell), severe psychomotor retardation, corneal clouding, and dystosis multiplex. These symptoms arise from a defect in the targeting of lysosomal enzymes due to an inability to carry out which of the following processes?
A. produce mannose-6-phosphate modifications in lysosomal enzymes
B. recycle the lysosomal receptor for mannose-6-phosphate present on lysosomal enzymes
C. remove mannose-6-phosphates from lysosomal enzymes prior to their transport to the lysosomes
D. synthesize the mannose-6-phosphate receptor found in lysosomes
E. transport mannose-6-phosphate receptors to lysosomes
Ans:
A. produce mannose-6-phosphate modifications in lysosomal enzymes