Kinetik der Dihydrofols�urereduktase aus Rattenleber und -gehirn mit 3-APADPH+H+ als Wasserstoffdonator

An enzyme preparation capable to reduce dihydrofolic acid to tetrahydrofolic acid, was prepared from liver and brain of rats. Using a spectrophotometric method the reaction rates of these preparations were determined. For rat liver dihydrofolic acid reductase K m was found to 2×10−6 M for NADPH + H+ and 1.8×10−6 M for FH2. Rat brain dihydrofolic acid-reductase has a K m of 8×10−6 M for NADPH + H+. Folic acid was shown to be a competitive inhibitor of the conversion of dihydrofolate to tetrahydrofolate. With 3-APADPH + H+ which is formed in brain of rats after application of 3-acetylpyridine, the enzyme activity of both preparations was found to be significantly decreased. These observations are discussed in relation to the functional impairment of rats treated with 3-acetylpyridine.