Isolation of N5N10-Methylene Tetrahydrofolate Reductase From Bovine Brain

Abstract
N5,N10 -methylene tetrahydrofolate reductase has been purified 100-fold from bovine brain. The initial fractionation with protamine sulfate and ammonium sulfate was followed by chromatography on DEAE-polyacrylamide gel (Bio Gel DM-30) and Sephadex G-200 as well as the selective adsorption and elution of the enzyme on calcium phosphate gel. The purified enzyme required FADH2 and catalyzed the reduction of the methylene group of N5,N10 -methylene tetrahydrofolate to the methyl group of N5 -methyl tetrahydrofolate. The pH optimum of the bovine brain reductase occurred at a pK of 6.5. The enzyme proved quite unstable. Both air oxidation and prolonged periods of storage at -20° inactivated the enzyme.

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