Zinc is a cofactor for more than 300 enzymes. Acrodermatitis enteropathica is an autosomal recessive condition due to defective zinc absorption. The protein mutated is:

• A Metallothionein-1 in enterocytes
• B ZnT1 (SLC30A1) zinc exporter from enterocytes to portal blood
• C Carbonic anhydrase-bound zinc chaperone
• D ZIP4 (SLC39A4) zinc transporter in duodenal enterocytes ✓

Explanation

Acrodermatitis enteropathica is caused by loss-of-function mutations in ZIP4 (SLC39A4), a zinc importer expressed on the apical surface of duodenal enterocytes that mediates zinc uptake from the intestinal lumen. Defective ZIP4 results in severe zinc malabsorption causing perioral and acral dermatitis, alopecia, immune dysfunction and growth retardation. ZIP (Zrt/Irt-like proteins) family transports zinc into cells, while ZnT family exports zinc from cells or into organelles. Metallothionein sequesters zinc intracellularly and is not responsible for absorption. ZnT1 exports zinc from enterocytes into portal blood and its loss would cause retention in enterocytes, not malabsorption.

Reference: Harper's Illustrated Biochemistry, 32nd ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.