30. Which one of the following is NOT involved with the absorption of iron in the intestine?
(1) Ferroportin 1
(2) Divalent metal transporter
(3) Hephaestin
(4) Transferrin
Iron absorption in the intestine is a tightly regulated process involving several key proteins that facilitate iron uptake, transport, and release into the bloodstream. Among these proteins, ferroportin 1, divalent metal transporter 1 (DMT1), and hephaestin play critical roles, whereas transferrin serves a different but related purpose.
Key Proteins Involved in Intestinal Iron Absorption
-
Ferroportin 1: This is the only known iron exporter located on the basolateral membrane of enterocytes. It transports iron from inside the cells to the interstitial fluid and ultimately into the bloodstream.
-
Divalent Metal Transporter 1 (DMT1): Located at the apical membrane, DMT1 mediates the uptake of ferrous iron (Fe2+) from the intestinal lumen into enterocytes.
-
Hephaestin: This is a multicopper oxidase enzyme associated with ferroportin. It oxidizes ferrous iron (Fe2+) to ferric iron (Fe3+) after it is exported by ferroportin. This oxidation is necessary because ferric iron binds to transferrin in the plasma for safe transport.
Role of Transferrin
Transferrin is a plasma glycoprotein responsible for transporting iron in the bloodstream to various tissues, such as the bone marrow for red blood cell production. However, transferrin is not directly involved in the absorption of iron by the intestinal epithelial cells. It acts after iron has been absorbed and released into the circulation.
Conclusion: Protein Not Involved with Intestinal Iron Absorption
Out of the proteins listed:
-
Ferroportin 1, DMT1, and hephaestin are directly involved in the intestinal absorption and transport of iron.
-
Transferrin functions in systemic iron transport post-absorption.
Therefore, the correct answer — the protein not involved in the absorption of iron in the intestine — is:
(4) Transferrin
