Further studies on the interaction of immobilized folate binding protein and enzyme-folate conjugates; an enzyme-linked competitive binding assay for folate

The kinetic and thermodynamic properties of the folate interaction with immobilized folate binding protein (FBP) are examined. The use of enzyme- rather than radio-labeled folate provides insight into the complex binding mechanism of folate with FBP and indicates that polymerization of the binding protein (evident for FBP-folate association in solution) is not a prerequisite for the cooperative behavior observed. An enzyme-linked competitive binding assay for folate based on this interaction is described and dose-response curves demonstrate the sensitivity and selectivity of the method. The accuracy of the assay is tested by determining folate in infant formula.