Iron-binding properties, amino acid composition, and structure of muscle tissue peptides from in vitro digestion of different meat sources.
BACKGROUND
The enhancing effect of meat on nonheme iron bioavailability in humans is thought to be due to the release of low-molecular-weight (LMW) iron-binding peptides during digestion.


OBJECTIVE
To better characterize the LMW iron-binding peptides from meat digests.


METHODS
Cooked beef, chicken, cod, lamb, and pork myofibrillar or sarcoplasmic protein extracts, casein, and egg albumin were digested in vitro with pepsin or pepsin/pancreatin. Ultrafiltrates were analyzed for N and iron and further characterized by gel filtration with added 59Fe, amino acid analysis, and LC-MS.


RESULTS
84% to 98% of total iron in enzymic digests was associated with soluble LMW peptides (< 10 kDa) of the myofibrillar proteins compared to only 2% to 20% in the corresponding sarcoplasmic protein digests. Pepsin digestion alone of the myobrillar proteins generated > 80% soluble LMW iron, compared to < 5% with casein and egg albumin. Iron-binding peptides from myofibrillar protein with an estimated 2 kDa molecular mass were separated by gel filtration. Peptides in this fraction were enriched in aspartic and glutamic acid residues and included potential peptide fragments of myosin.


CONCLUSIONS
LMW (< 10 kDa) peptides in enzyme digests of myofibrillar proteins were the major facilitators of iron solubility. Unlike with casein, egg albumin, and most sarcoplasmic proteins, these LMW peptides were generated on pepsin digestion. One group of iron-binding peptides had a mass of approximately 2 kDa and was enriched in glutamic and aspartic acids. Such early generation of a multitude of LMW iron-binding peptides could explain the enhancing effect of muscle tissue on iron absorption.
Storcksdieck genannt Bonsmann
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Inst. of Food Science and Nutrition, ETH Zurich, 8092 Zurich, Switzerland. stefan.storcksdieck@ilw.agrl.ethz.ch
Storcksdieck
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Bonsmann
Genannt
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Hurrell
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RF
D000596:Amino Acids / Q000032:analysis*; D000818:Animals; D001682:Biological Availability; D002417:Cattle; D002645:Chickens; D004063:Digestion; D005374:Filtration; D048389:Gadus morhua; D006801:Humans; D007408:Intestinal Absorption; D019266:Iron, Dietary / Q000493:pharmacokinetics*; D033862:Iron-Binding Proteins / Q000494:pharmacology*; D008460:Meat / Q000032:analysis*; D008970:Molecular Weight; D009124:Muscle Proteins / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000378:metabolism; D012756:Sheep; D012995:Solubility; D013045:Species Specificity; D013552:Swine
D000596:Amino Acids; D019266:Iron, Dietary; D033862:Iron-Binding Proteins; D009124:Muscle Proteins