Hydrolysis of a phosphonate ester catalyzed by an enzyme from Dictyostelium discoideum.

An activity capable of hydrolyzing the phosphonate ester, 4-nitrophenyl phenylphosphonate has been detected in the eucaryotic microorganism Dictyostelium discoideum. This activity (4-nitrophenyl phenylphosphonate-esterase) was found in both membrane-enriched and soluble fractions. Two other activities present in this fraction, namely cyclic AMP-diesterase and an ATP-hydrolase, did not copurify with the 4-nitrophenyl phenylphosphonate-esterase. Also while ATP and cAMP inhibited the hydrolysis of 4-nitrophenyl phenlyphosphonate, they did so in a noncompetitive manner and, furthermore, saturating concentrations of 4-nitrophenyl phenylphosphonate had no effect on the hydrolysis of either cyclic AMP or ATP. The partially purified preparation was more active at pH 7 than at either pH 5 or 9, more active with acetate than chloride, and more active at 22 °C than at either 12 or 30 °C. The activity is inhibited by AMP in a competitive manner, but is not affected by levamisole, an inhibitor specific for alkaline phosphatase activity.