Haem in the gut. I. Fate of haemoproteins and the absorption of haem.

Abstract

Haem (FeII-protoporphyrin-IX) is presented to the gut lumen as haemoproteins derived from exogenous dietary) and endogenous (mucosal cell desquamation and bleeding) sources. Haemoproteins such as haemoglobin, myoglobin and catalase undergo hydrolysis by luminal proteases to release the haem. Released haem is maintained in a soluble form in the gut lumen by the products of haemoprotein digestion. Chelators of elemental iron do not bind haem-iron and so haem-iron is better absorbed than elemental iron. Haem-iron does not exchange with luminal elemental iron. Mucosal uptake of haem is limited. Less than 10% binds to the brush border of the villus cell. Although the mechanisms by which haem bind..