Affinity and rate constants for interactions of bovine folate-binding protein and folate derivatives determined by optical biosensor technology. Effect of stereoselectivity.
The interactions between bovine folate-binding protein (FBP) and different folate derivatives in pure diastereoisomeric forms were studied at pH 7.4 by a surface plasmon resonance technology (Biacore). The results show that folic acid had the most rapid association rate (k(a) = 1.0 x 10(6) M(-)(1) s(-)(1)), whereas (6S)-5-HCO-5,6,7,8-tetrahydrofolic acid had the most rapid dissociation rate (k(d) = 3.2 x l0(-)(3) s(-)(1)). The equilibrium dissociation constant (K(D)), calculated from the quotient of k(d)/k(a), showed that the two forms of folates not occurring in nature, that is, folic acid and (6R)-5-CH(3)-5,6,7,8-tetrahydrofolic acid, had the highest affinities for FBP, 20 and 160 pmol/L, respectively. The results thus show that there were great differences in the interactions between folate-binding protein and the major forms of folate derivatives. The nutritional implications of these differences are discussed.
Nygren-Babol
Linnéa
L
Department of Food Science, Swedish University of Agricultural Sciences, Uppsala.
Sternesjö
Ase
A
Jägerstad
Margareta
M
Björck
Lennart
L
D002352:Carrier Proteins / Q000378:metabolism*; D058973:Folate Receptors, GPI-Anchored; D005492:Folic Acid / Q000031:analogs & derivatives* / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D011956:Receptors, Cell Surface / Q000378:metabolism*; D013237:Stereoisomerism; D020349:Surface Plasmon Resonance; D013763:Tetrahydrofolates / Q000378:metabolism
D002352:Carrier Proteins; D058973:Folate Receptors, GPI-Anchored; D011956:Receptors, Cell Surface; D013763:Tetrahydrofolates; D005492:Folic Acid; C005984:5-methyltetrahydrofolate