New Carrier Protein(s) of Folic Acid in Human Serum

Markkanen, T; Pajula, Raija; Virtanen, Sari; Himanen, P

doi:10.1159/000208450

Cited by 23 publications

(21 citation statements)

References 6 publications

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“…activity" appeared in the a2-macroglobulin and transferrin regions (14). More recently several laboratories have described some properties of "serum folate binder" from a few patients with chronic granulocytic leukemia (2) or folate deficiency (3) and from some pregnant women and women taking oral contraceptives (15).…”

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 earlier been reported from our laboratory that, in Sephadex gel chromatography, some 30-40% of the folic acid activity (FAA) of the serum is bound to serum proteins and the balance is eluated 'free' after the separation of proteins [4][5][6][7]. It is possible, however, that some of the FAA bound to proteins in vivo is split off during chromatography.…”

Section: Carrier Proteins Folic Acid Metabolism Gel Chromatography Trmentioning

confidence: 99%

“…The result could be reproduced and confirmed. When the analysis of the protein-bound FAA was continued it was seen that the majority, some 40-50%, in DEAE-Sephadex chromatography was bound to a-2-macroglobulin [7]. This finding also proved to be constant and reprodu cible.…”

mentioning

confidence: 98%

Transferrin, the Third Carrier Protein of Folic Acid Activity in Human Serum

Markkanen¹,

Virtanen²,

Himanen³

et al. 1972

Acta Haematol

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“…The main endogenous binder is chromatographically albumin-associated [8,13,19,20] on DEAE-A50 columns, although minor binders associated with a2-macroglobulins [21] and even transferrin [22] have been suggested. After dissociating folate at acid pH from cord serum binder, Kamen and Caston [9] found a denuded protein with molecular mass of 40,000, a binding preference for PteGlu rather than CH3H4PteGlu, but a binding capacity only 10% of the original serum binder.…”

Section: Discussionmentioning

confidence: 99%

Comparison between the Unsaturated Plasma Folate Binder and <i>in vivo</i> Labelled Plasma Folate Binder

Retief¹,

Ad²,

Oosthuizen³

et al. 1978

Acta Haematol

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Endogenous plasma folate binder denuded of folate by dialysis at pH 3, subsequently bound more methylfolate than folic acid, in contrast with the minor unsaturated plasma binder which bound folic acid in preference to methylfolate. On Sephadex DEAE-A50 chromatography ¹⁴C-CH₃H₄PteGlu bound to acid-denuded endogenous binder, eluted like the endogenous binder-radioactivity, labelled in vivo after oral ¹⁴C-CH₃H₄PteGlu. It is suggested that the endogenous plasma folate binder is not identical with the unsaturated binder.

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New Carrier Protein(s) of Folic Acid in Human Serum

Cited by 23 publications

References 6 publications

Purification of folate binding factor in normal umbilical cord serum.

Purification of folate binding factor in normal umbilical cord serum.

Transferrin, the Third Carrier Protein of Folic Acid Activity in Human Serum

Comparison between the Unsaturated Plasma Folate Binder and <i>in vivo</i> Labelled Plasma Folate Binder

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