Purification and characterization of tetrahydrofolate.protein complex in bovine liver

Gel filtration of bovine liver extract on a Sephadex G-200 column resolved three macromolecular fractions with dihydropteridine reductase-dependent cytochrome c reducing activity. One of the active fractions was purified from the extract through the steps of solvent fractionation, chromatography on DEAE-Sephadex, and gel filtration. Biochemical and microbiological analyses showed that the purified complex consists of a Mr = 70,000 protein and tetrahydropteroyldiglutamate. In contrast to the extreme lability of free tetrahydropteridines the complex was quite stable against autooxidation under aerobic conditions.