title: Ferric reductase activity of low molecular weight human milk fraction is associated with enhanced iron solubility and uptake in Caco-2 cells.
abstract: It is known that the fractional absorption of extrinsic iron from human milk is higher in infants and adults. A low molecular weight milk fraction has been proposed to increase the bioavailability of iron from human milk. Nevertheless, the mechanisms remained elusive. Here in we demonstrate ferric reductase activity (Km7.73x10(-6)M) in low molecular weight human milk fraction (10kF, filtrate derived from ultra filtration of milk whey through 10kDa cutoff membrane), which increased ferric iron solubility and iron uptake in Caco-2 cells. The 10kF fraction was as effective as ascorbic acid (1:20 iron to ascorbic acid) in increasing the ferric iron solubility and uptake in Caco-2 cells. Further, gel filtration chromatography on peptide column led to co-elution of ferric reductase and iron solubilization activities at an apparent molecular mass of <1500Da. Interestingly, only these fractions containing ferric reductase activity also stimulated the uptake of iron in Caco-2 cells. Thus, it is concluded that human milk possesses ferric reductase activity and is associated with ferric iron solubilization and enhanced absorption.
authors.affiliation: Micronutrient Research Group, Biophysics Division, National Institute of Nutrition (ICMR), Jamai Osmania, Tarnaka, Hyderabad, Andhrapradesh 500 604, India. raghu_nin2000@yahoo.com
authors.forename: Raghu
authors.initials: R
authors.lastname: Pullakhandam
authors.forename: Madhavan Krishnapillai
authors.initials: MK
authors.lastname: Nair
authors.forename: Sunanda
authors.initials: S
authors.lastname: Kasula
authors.forename: Sreenivasulu
authors.initials: S
authors.lastname: Kilari
authors.forename: Tippeswamy Gowda
authors.initials: TG
authors.lastname: Thippande
mesh_terms: D018938:Caco-2 Cells; D038181:FMN Reductase / Q000378:metabolism*; D006801:Humans; D007501:Iron / Q000378:metabolism*; D008895:Milk, Human / Q000201:enzymology*; D008970:Molecular Weight; D012995:Solubility
chemical_list: D007501:Iron; D038181:FMN Reductase; C023903:ferric citrate iron reductase