Nov 1, 1975

Purification of folate binding factor in normal umbilical cord serum

Proceedings of the National Academy of Sciences of the United States of America
B A Kamen, J D Caston

Abstract

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-methyltetrahydro...Continue Reading

  • References9
  • Citations29

References

Mentioned in this Paper

Sephadex G 200
Entire Fetus
Derivatives
Chromatography
Folate Serum
Acidification - ActCode
Umbilical Cord Structure
Tetrahydrofolates
Adsorption
Activated Charcoal

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