Binding of Folic Acid and Derivatives by Milk

Abstract

Cow’s milk was found to contain a fraction that binds pteroylglutamate (PGA) rapidly and irreversibly. It also binds Teropterin, tetrahydrofolic acid, and 5-methyltetrahydrofolic acid, but not other folic acid derivatives tested. This binder can be utilized in isotope dilution methods for PGA and to assess the purity of radioactive PGA. Another milk fraction, perhaps an enzyme, appears to be responsible for the binding of folinic acid in a reversible manner.