100] Kinetics of folate-protein binding

Abstract

Publisher Summary This chapter discusses the kinetics of folate-protein binding. In mammals, folate-(pteroylglutamate-)binding proteins have been demonstrated in cow's milk and human milk, hog kidney, rat liver, rabbit choroid plexus, intestinal brush border membrane from rat, leukemic cells, and in human serum and animal serum as well. Investigations of the kinetics of folate binding to protein need a method that separates protein-bound and free folate, without affecting the equilibrium between them. Adsorption of free folate to the charcoal method is predominant in the competitive radioassay methods for the determination of folate in serum where the folate-binding protein in milk has been used. It has the advantage of being quick and practical. However, it has many disadvantages: (1) in order to ensure that only free folate is bound to charcoal, the particles must be coated with various macromolecular substances, such as dextrane, albumin, or hemoglobin that act as a molecular sieve, (2) by ultrafiltration method, it is possible to obtain a good separation of free and bound folate if neither is bound to the membrane. The method has been used for investigating the binding of folate to milk protein and for an investigation of the binding of folate to serum proteins and to pure albumin preparations.