Binding Added Iron to Various Milk Proteins

Abstract

Binding of an added radionuclide to milk protein and casein components of cow's milk fractionated by the combination of Sephadex G-150 gel filtration and diethylaminoethyl-cellulose chromatography was determined. Iron-59 labeled ferric chloride was added directly to raw whole milk at a concentration of .02 and 10 ppm isotope and carrier, respectively, and held overnight at 4 C. Five milliliters of the skin milk were chromatographed on a Sephadex G-150 column and fractionated into casein, whey protein, and nonprotein materials. The casein fraction was chromatographed on a diethylaminoethyl-cellulose column and separated into its components, alphas-, beta-, and kappa-caseins. Casein bound about 85% of the added iron in skim milk; of this amount, 72, 21, and 4% were associated with the alphas-, beta, and kappa-caseins.

Reduction of iron/zinc interactions using metal bound to the caseinophosphopeptide 1–25 of β-casein

“…Preparation of the 1-25 caseinophosphopeptide of B-casein (R CN (l-25)) 13 Casein was isolated from industrially-produced sodium caseinate (Armor Proteines, Saint-Brice-en-Cog&, France) by cold solubilization (pH 4,5 ; 4"C), followed by ion exchange chromatography (15,17,19). O-CN (l-25) was obtained by tryptic digestion of 6 casein.…”

“…D-CN (l-25) is a well defined phosphopeptide produced by the hydrolysis of D-casein, which has four of the five phosphoserine residues of the native protein. These residues can bind divalent cations such as Fe, Zn or calcium in proportion to their degree of phosphorylation and according to the cation (16)(17)(18). Thus 1 mole of D-CN (l-25) can bind 4 moles of Fe or Zn with a greater affinity than for calcium (18).…”

Aluminium content of Spanish infant formula

“…Supplementation with Fe (II) results in a formula with high iron content in the fat fraction (Hegenauer et al 1979) whereas if Fe(III) is used, the iron is bound to casein micelles (Demott and Dincer, 1976). Probably, the existing correlation in whole-milk-based formulae (p = 0.010) could correspond with the different chemical form used in iron supplementation and the technological process used by manufacturers.…”

Absorption digestive du fer lié au caséinophosphopeptide 1-25 de la β-caséine

“…Il est lui-même partiellement résistant aux enzymes digestives et soluble dans le milieu intestinal (Sato et al, 1986 ;Bouhallab et al, 1991 ;Brommage et al, 1991). Les résidus phosphorylés des caséines fixent le calcium et le maintiennent à l'état soluble dans l'intestin (Sato et al, 1986 ;Yuan et Kitts, 1991) ; ils ont éga-Iement la capacité de fixer d'autres cations divalents à la place du calcium, proportionnellement à leur degré de phosphorylation et en fonction du cation (Demott et Dincer, 1976 ;Brulé et Fauquant, 1982 ;West, 1986 ;Causeret, 1986 ;Bouhallab et al, 1991). Le~-CN (1-25) possède quatre des cinq phosphosérines de la protéine native: 1 mole peut fixer 4 moles de fer, avec une affinité 100 fois plus forte que pour le calcium (Bouhallab et al, 1991).…”