ENADE Ciências Biológicas Practice Questions - ENADE Ciências Biológicas - Bacharelado And Licenciatura Exam

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In human cellular pathology, I-cell disease (mucolipidosis type II) is a severe autosomal recessive disorder characterized by the absence of multiple hydrolytic enzymes in lysosomes and their aberrant hypersecretion into the extracellular fluid. What is the underlying biochemical defect causing this cellular phenotype?

Constitutive activation of dynamin GTPase, resulting in premature fusion of late endosomes with the mitochondrial outer membrane. Defect in the Sec61 translocon channel, preventing the entry of newly synthesized acid hydrolases into the lumen of the rough endoplasmic reticulum. Total absence of the vacuolar H+-ATPase (V-ATPase) proton pump in the lysosomal membrane, leading to an alkaline lysosomal lumen. Mutation in the gene encoding UDP-N-acetylglucosamine:lysosomal-enzyme N-acetylglucosaminyl-1-phosphotransferase, preventing the generation of mannose-6-phosphate (M6P) targeting signals in the cis-Golgi.

Correct Answer:

Mutation in the gene encoding UDP-N-acetylglucosamine:lysosomal-enzyme N-acetylglucosaminyl-1-phosphotransferase, preventing the generation of mannose-6-phosphate (M6P) targeting signals in the cis-Golgi.

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