Mannose-6-phosphate and lysosomal targeting
In I-cell disease, the Golgi fails to add mannose-6-phosphate to lysosomal enzymes. What happens to those enzymes?
Answer C: explanation for every choice
A
Lysosomal enzymes have no nuclear localization signal.
B
Retention in the ER requires an ER retention signal such as KDEL.
C
Correct. Without the mannose-6-phosphate tag, the enzymes follow the default secretory pathway, leaving lysosomes without them.
D
Properly folded enzymes pass through the ER normally. The defect occurs in the Golgi.
TakeawayMannose-6-phosphate sends enzymes to lysosomes. Without it, they're secreted.
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Reviewed 2026-11-05 by a medical student. Spot an error? Report it with question ID bb108.