High-affinity binding of folate to a protein in serum of male subjects.
The binding pattern of [3H]folate in the serum of male subjects was studied in equilibrium dialysis experiments (pH 7.4, 37 degrees C). It was possible to distinguish between a high (association constant, Kass = 10(10) (mol/l)-1; maximum binding of folate = 0.6 nmol/l) and a low affinity type of binding. The high-affinity binder was a trace protein (molecular size approximately 35 000) which was eluted with 30 mmol/l NaC, (pH 6.3) from serum subjected to DEAE-Sepharose CL-6B chromatography. The low-affinity binding activity mainly associated with albumin was eluted with 1 mmol/l NaCl. High-affinity binding was depressed at 7 degrees C (Kass = 10(9) (mol/l)-1). Furthermore, methotrexate acted as a weak inhibitor  of high-affinity binding, the molar methotrexate/folate ratio being 100/1 at 50% inhibition.
D002852:Chromatography, Ion Exchange; D003956:Dialysis; D005492:Folic Acid / Q000097:blood*; D006801:Humans; D007700:Kinetics; D008297:Male; D008970:Molecular Weight; D011485:Protein Binding
D005492:Folic Acid