Formic Acid Activation in Plants. I. Purification, Properties and Distribution of Formyltetrahydrofolate Synthetase

Abstract

The formate-activating enzyme, formyltetrahydrofolate synthetase, was found in every plant tissue examined for its presence. The enzyme is associated with the soluble phase of the cytoplasm. Eighty-fold purification was obtained with ammonium sulfate fractionation, calcium phos -phate gel adsorption, and DEAE cellulose column chromatography. The Michaelis constant values with respect to formate, ATP,anddl-tetrahydro-folate were calculated to be 3.3 x 10-2 M, 9 x 10-5 M, and 9.2 x 10-4 M, respectively. The optimum pH for enzyme activity was 7.5 -8.5. The enzyme lost activity rapidly when stored at 0[degree] in the absence of reducing agents, but could be stored for several weeks with little loss of activity at -15[degree] in 0.01 M mercaptoethanol at pH 7.5 - 8.0.