Potato pyrophosphatases

Abstract

Potatoes contain a labile alkaline pyrophosphatase (PP-ase) besides the already known acid phosphatase and acid pyrophosphatase. No alkaline phosphatase could be demonstrated. The alkaline PP-ase is active only in the presence of 0.01-0.02 [image]Mg++. The alkaline PP-ase is destroyed at acid pH while the acid enzymes are inactivated at alkaline pH. Fractionation with ethanol or acetone resulted in total destruction of alkaline PP-ase; acid enzymes were unaffected. Alkaline PP-ase could be purified only by fractionation with ammonium sulfate. Molybdate and tungstate strongly inhibited acid enzymes while alkaline PP-ase was unaffected. Ca++ had no effect on acid enzymes but inhibited the alkaline enzyme. Fluoride was toxic to all the enzymes. Formaldehyde inhibited the alkaline enzyme, indicating that intact amino groups are essential for its action. The alkaline PP-ase is probably not a SH-enzyme, as there was neither activation by cysteine nor inhibition by mapharside. Data on the reaction rates, Michaelis constants and energies of activation for the 3 enzymes are presented.