THE DISTRIBUTION OF FORMYLTETRAHYDROFOLATE SYNTHETASE IN PLANTS, AND THE PURIFICATION AND PROPERTIES OF THE ENZYME FROM PEA SEEDLINGS1

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Abstract
Formyltetrahydrofolate synthetase (E. C. 6. 3. 4. 3) was found to be widely distributed in higher plants and the high enzyme activity was observed in green leaves of Brassica and Allium species, spinach, and in pea seedlings. In pea seedlings, the enzyme activity changed during the course of germination, and most of the enzyme activity was located in a soluble fraction of the cytoplasm. The enzyme was labile and lost the activity rapidly, even when stored at 5° in the presence of 0.1 M mercaptoethanol. It was, however, found that ammonium sulfate was very effective in stabilizing the enzyme activity. The enzyme has been purified approximately 500-fold from extracts of pea seedlings by treatments with ammonium sulfate, protamine sulfate, hydroxylapatite, calcium phosphate gel, and DEAE-cellulose column chromatography. The purified enzyme was specific for formate, ATP and FAH4, and the Michaelis constants for these reactants were 2.1 × 10−2 M, 5.1 × 10−4 M, and 5.6 × 10−3 M, respectively. The optimum pH was found to be 8.0, and the optimal temperature was observed at 37°. Both NH4$ and a divalent cation (MgSS or MnSS) were required for the optimal activity.

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