Carrier Proteins of Folic Acid Activity in Human Serum

Markkanen, T; Peltola, O.

doi:10.1159/000208613

Cited by 30 publications

(30 citation statements)

References 5 publications

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“…Also, Ford and Salter reported some of the properties of unsaturated binder in bovine and human milk (12). Markkanen et al (13) demonstrated that serum folate, as judged by growth of Lactobacillus casei in a microbiological assay, fractionated on Sephadex G-200 into three bands of high molecular weight in addition to the major low-molecularweight fraction that corresponded to "free" folate. When chromatographed on DEAE-Sephadex A-50, the "L. case4…”

Section: Resultsmentioning

confidence: 99%

Purification of folate binding factor in normal umbilical cord serum.

Kamen¹,

Caston²

1975

Proc. Natl. Acad. Sci. U.S.A.

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Human umbilical cord serum was found to contain both free folate and folate complexed to a high-molecular weight factor. The complexed folate was bound to a very high affinity binder and was present in concentrations equivalent to as much as 60 ng of 5-methyltetrahydrofolic acid per ml of serum. Acidification of the serum caused disassociation of the folate-binder complex. Released folates were separated from binder by Sephadex gel filtration, zonal centrifugation through sucrose gradients, or adsorption onto activated charcoal. The separated binding factor, either saturated or unsaturated with folate, had a molecular weight of about 40,000 on Sephadex G-200 chromatography. Binding of [3H]pteroylglutamic acid was rapid and, as in the original endogenous folate-binder complex, was essentially irreversible at neutral pH. The affinity and specificity of the binder were examined by competition experiments using [3H]pteroylglutamic acid and nonradioactive folate derivatives. Oxidized folates were bound in preference to reduced derivatives, but only three to four times more unlabeled 5-methyltetrahydrofolic acid than pteroylglutamic acid was required to produce an equal level of competition. The strong affinity for 5-methyltetrahydrofolic acid, the main serum folate, suggests that the binder could be part of the mechanism by which the fetus concentrates maternally supplied folate for its growth and development.

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Section: Resultsmentioning

confidence: 99%

Purification of folate binding factor in normal umbilical cord serum.

Kamen¹,

Caston²

1975

Proc. Natl. Acad. Sci. U.S.A.

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“…It has recently been established that a fraction of human serum fol ates is bound to proteins [11] and that part of this fraction is firmly bound to a specific binding protein [15]. This fraction possibly cannot be determined by the radioassay technique but it could be used by L. casei.…”

Section: Discussionmentioning

confidence: 99%

Radioassay of Serum Folate with Use of Pig Plasma Folate Binders

Mantzos¹

1975

Acta Haematol

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Pig plasma has been used as a source of specific folate binders for the development of a rapid radioassay to measure the concentration of folate in serum. The assay uses ³H-pteroylglutamic acid as tracer and N-5-methyltetrahydrofolic acid for the construction of the standard curve. The assay is run in a two-step incubation system of 15 min each at room temperature. Comparison between the results obtained with this method and a microbiological one indicated that for sera with relatively high folate levels there was a good agreement between the two methods, whereas for sera with low folate levels the present method produces lower values than the microbiological one. The diagnostic value of the results obtained by the two methods is discussed on the basis of the availability to the tissues of the folates which are firmly bound to specific folate binders of human serum.

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“…The supernatant (40 ml) of the liver suspension was then fractionated immediate ly in column chromatography (Sephadex G-200, Pharmacia, Uppsala), using tech niques described earlier [6]. In each chromatography, 180 samples (10 ml) were collected, and the 3H-activity as well as the microbiological FAA of every sample were measured.…”

Section: Methodsmentioning

confidence: 99%

“…The proteins of both the supernatant of the liver suspension and its chroma tography fractions were determined with the biuret method, and the folic acid with the L. casei method (after the addition of ascorbic acid) as reported earlier [6]. Samples (0.2 ml) of the supernatant of the liver suspension and its chromato graphy fractions were taken into scintillation flasks for the determination of 3H-activity.…”

Section: Methodsmentioning

confidence: 99%

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Binding of Folic Acid to Serum Proteins

Markkanen¹,

Rl²,

Virtanen³

et al. 1975

Acta Haematol

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Sephadex G-200 chromatographies of the liver cell sap of rabbits, 1, 3 and 6 days after an injection of ³H-folic acid activity (FAA) into the circulation, were used in an attempt to study the binding of this labelled FAA to liver proteins. The labelled FAA was quickly accumulated in the liver, and in the cell sap it was grouped chromatographically to two maxima, which corresponded to the two maxima of microbiological FAA (L. casei). The maxima were eluated in the chromatography together with cell sap proteins. The possible coupling of FAA to proteins in the liver is discussed.

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Carrier Proteins of Folic Acid Activity in Human Serum

Cited by 30 publications

References 5 publications

Purification of folate binding factor in normal umbilical cord serum.

Purification of folate binding factor in normal umbilical cord serum.

Radioassay of Serum Folate with Use of Pig Plasma Folate Binders

Binding of Folic Acid to Serum Proteins

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