Binding of Iron to Amino Acids and Serum Proteins in Vitro

Prasad, Ananda S.; Oberleas, Donald

doi:10.3181/00379727-138-36021

Cited by 60 publications

(69 citation statements)

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“…Amino acid-bound Zn is important in some higher pH biological solutions. For example, Zn coordination with amino acids has been demonstrated in human blood serum (pH 7.4), where Znamino acid complexes are part of a "labile pool" of Zn (12).…”

Section: Cd2+(ca)mentioning

confidence: 99%

Metal Complexation in Xylem Fluid

White¹,

Baker²,

Chaney³

et al. 1981

Plant Physiol.

145

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Theoretical considerations of metal complex formation in aqueous solutions were used to develop a computer program (CHELATE) to cakulate all equilibrium species (free metal ions, metal complexes, etc.) in any user-defined system, such as xylem fluid. Mass-balance equations were established to describe each free metal ion and each free ligand concentration as a function of solution pH, total metal or total ligand, hydrogen-association constants, and the stability constants of known metal complexes. A default data base can be altered by the user to define any desired system covered by the stored equilibrium data. The program can currently handle nine metal ions, 35 ligands, and 500 complex species. The validity of the program was confirmed by using experimental test systems in which free-metal ion activity measurements were made with ion-selective electrodes. Program CHELATE was used to calculate the distribution of six metals in 0-to 1-hour exudate from soybean (Glycine max L. Meff.) and tomato (Lycopersicon escuentum Mill.) plants grown in normal and Zn-phytotoxic nutrient solutions. The results indicated that Fe is bound by citric acid, and Cu is bound by several amino acids in the normal-Zn exudate. Most of the Cu in soybean exudate is bound to asparagine and histidine. In tomato, Cu is bound to histidine, glutamine, and asparagine. Zinc, Mn, Ca, and Mg are bound primarily by citric acid and malic acid in both species; the per cent bound for these metals is lower than that for Fe and Cu. Zinc phytotoxicity caused equilibrium concentration shifts and resulted in the formation of several adtional metal complexes not found in the normal-Zn exudate. Work reported in a companion paper (24) showed that xylem ' This work represents cooperative research from the fluid contains many natural complexing compounds and indicates that metal ions should form metal complexes in vivo in the xylem sap. There is in vitro electrophoretic evidence for stable metal complex formation in xylem fluid (2, 20, 23) but no quantitative estimates of the equilibrium distribution of metals, ligands, metal complexes, and other solutes. In a solution containing several metals and ligands, simultaneous competing equilibria distribute the metals among the ligands, creating numerous complexes. Such a system can be described both qualitatively and quantitatively; however, quantification of all equilibrium species in a multimetal, multiligand system is far more difficult than listing the theoretically permissible (qualitative) species. Although many aqueous species cannot be measured, equilibrium chemistry can be used to estimate metal binding in aqueous solutions. The degree to which hydrated metal ions associate with various ligands depends primarily on the relative metal and ligand concentrations , solution pH, and the pertinent empirically determined stability constants. These variables have been used to determine equilibrium distributions of metals among ligands in several diverse natural aqueous solutions (6, 9, 21). Most of these systems are...

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Section: Cd2+(ca)mentioning

confidence: 99%

Metal Complexation in Xylem Fluid

White¹,

Baker²,

Chaney³

et al. 1981

Plant Physiol.

145

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“…About 99 % of this is protein bound, about 85 % loosely bound to albumin, and 15 % tightly bound to L2-macroglobulin (Giroux, 1975;Foote & Delves, 1984). The remaining 1 % is ultrafilterable, and bound to low molecular weight compounds (Prasad & Oberleas, 1970;Giroux & Henkin, 1972). Computer simulation indicates that cysteine, citrate and histidine are mainly involved (May, Linder & Williams, 1977).…”

mentioning

confidence: 99%

The mechanism of zinc uptake by cultured rat liver cells.

Taylor

Simons

1994

The Journal of Physiology

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1. The initial rate of 65Zn uptake into cultured rat hepatocytes has been measured over a range of Zn2+ concentrations from 3 x 10(‐10) M to 5 x 10(‐6) M. Histidine and albumin were used to buffer Zn2+ ions at concentrations below 1 x 10(‐6) M. 2. The results suggest there are two mechanisms for Zn2+ uptake; a high‐affinity, saturable pathway, with a maximum velocity (Vmax) of 20‐30 pmol (mg protein)‐1 min‐1 and a Michaelis‐Menten constant (Km) of about 2 x 10(‐9) M Zn2+ (with histidine), and a low‐affinity, linear pathway, that only makes a significant contribution to Zn2+ uptake at Zn2+ concentrations above 1 x 10(‐6) M. 3. Transport via the high‐affinity pathway is dependent on the concentration of Zn2+ ions and not on the concentrations of Zn(2+)‐ligand complexes, suggesting that Zn2+ is the transported species. 4. The affinity of the saturable pathway for Zn2+ is slightly lower in the presence of albumin, with a Km of about 1.3 x 10(‐8) M. The reason for this is uncertain.

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“…Inadequate dietary zinc intake cannot account for the lowered PZn levels observed in our FAS patients since PZn deficiency did not occur in any of the six control subjects with comparable dietary intake. PZn levels are known to be dependent on plasma protein concentration since approximately 80 to 90% of zinc is bound to protein, mainly albumin (20). In this regard, plasma protein concentrations in FAS patients (6.8 & 1.1 g/dl) were similar to those of controls (7.1 _+ 1.4 g/dl) (p = NS).…”

Section: Discussionmentioning

confidence: 83%

Zinc Status of Infants with Fetal Alcohol Syndrome

Assadi

Ziai

1986

Pediatr Res

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ABSTRACT. Plasma and urinary zinc levels were examined in 6 infants with fetal alcohol syndrome to determine whether zinc deficiency, if present in fetal alcohol syndrome patients, is secondary to an increased urinary zinc excretion. Six infants born to nonalcoholic mothers served as controls. There was no significant difference in creatinine clearance, urine flow rate, or plasma albumin concentrations between the two groups. Plasma concentrations of zinc were significantly lower in fetal alcohol syndrome patients (62.

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Binding of Iron to Amino Acids and Serum Proteins in Vitro

Cited by 60 publications

References 0 publications

Metal Complexation in Xylem Fluid

Metal Complexation in Xylem Fluid

The mechanism of zinc uptake by cultured rat liver cells.

Zinc Status of Infants with Fetal Alcohol Syndrome

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