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A STUDY OF IRON BINDING BY SOY PROTEIN
Abstract
The availability of iron in the presence of soy proteins was studied using an everted rat gut assay and an ultrafiltration procedure. Polyacrylamide gel electrophoresis (PAGE) and gel filtration chromatography were used to characterize iron binding of a soy isolate. Soy products inhibited the free uptake of iron by everted gut tissue with soy isolate inhibiting iron absorption more than soy flour. When soy protein was in the incubating buffer, approximately 10% of the iron was either transported to the interior of the gut sac or adhered to the gut tissue itself compared to approximately 30% when soy protein was not present in the incubating buffer. A soy protein-iron complex was ultrafiltered using a membrane with a 10,000 molecular weight cut off. The pH of the sample was raised stepwise from pH 5.0 to 7.5 during ultrafiltration. The membrane retained 12% of the iron when a control, which contained no protein, was ultrafiltered. When soy protein was added to the iron solution, 70% of the iron was retained by the membrane. To isolate the iron containing protein or peptide segments of soy protein isolate, the protein-iron complex, retained by the ultrafiltration membrane, was partially digested with trypsin. Polyacrylamide gel electrophoresis (PAGE) stripped the iron from the protein, and the iron migrated independently through the gel. Gel filtration chromatography showed that the iron was bound to large molecular weight peptides and to the undigested soy protein isolate. When NaCl was added to the elution buffer and 1,10-phenanthroline was incubated with the protein-iron complex, 95% of the iron could be removed from the large molecular weight peptides and 75% of the iron from the undigested soy protein isolate. The presence of large amounts of soy isolate in the diet may reduce iron absorption in the intestine by carrying iron past the major sites of iron absorption before being released from the soy protein by digestion.
Subject Area
Food science
Recommended Citation
SCHNEPF, MARILYNN IRENE, "A STUDY OF IRON BINDING BY SOY PROTEIN" (1984). ETD collection for University of Nebraska-Lincoln. AAI8423827.
https://digitalcommons.unl.edu/dissertations/AAI8423827