RESUMO
Hephaestin (Hp) plays an important role in intestinal iron absorption and is predicted to be a ferroxidase based on significant sequence identity to the serum multicopper ferroxidase ceruloplasmin. Here, we demonstrate that Hp has both amine oxidase and ferroxidase activity in cultured cells and primary intestinal enterocytes with the use of both gel and solution assays. The specificity of the activity is shown by immunoblotting, immunoprecipitation, and immunodepletion experiments. Surprisingly, the truncated hephaestin expressed in sex-linked anemia (sla) mice still has measurable, but decreased, oxidase activity. Molecular modeling of the truncated hephaestin suggests retention of a minimum catalytic core required for enzymatic activity. We suggest that hephaestin, by way of its ferroxidase activity, facilitates iron export from intestinal enterocytes, most likely in cooperation with the basolateral iron transporter, Ireg1.
