Influence of the Extent of Haemoglobin Hydrolysis on the Digestive Absorption of Haem Iron in the Rat. an in Vitro Study

Abstract

This study was designed to assess the haem‐peptide interactions which occur during progressive haemoglobin hydrolysis by digestive enzymes and their relationship with haem iron digestive absorption. The behaviour of different haemoglobin hydrolysates was studied using the Ussing chamber model. Hydrolysates were produced from enzyme digestion of bovine haemoglobin at pH 3 by pepsin and at pH 10 by subtilisin. Samples with increasing degrees of hydrolysis (0‐15%) were studied. Biochemical assays (pyridine haemochromogen method and UV absorption spectra) were used to follow haem solubility and haem‐peptide interactions in samples. Increasing the hydrolysis level of haemoglobin was associated with an enhanced iron uptake; the highest uptake rate was reached between 8 and 11% of globin hydrolysis, whichever enzyme was used. The mechanisms rendering iron soluble and available differ between the two enzymes. The comparison between biochemical and absorption data suggests that the formation of soluble peptide‐haem complexes was not sufficient to enhance haem iron absorption, since globin‐bound iron is poorly absorbed; an efficient absorption occurred only when haem was loosely bound to low molecular weight peptides.