ACID PYROPHOSPHATASE FROM RED KIDNEY BEANS

Partial purification of acid pyrophosphatase activity from dried red k idney beans was achieved. The crude enzyme was found to adhere to plas tic and was very unstable. These problems were solved by extraction wi th low pH and high-ionic-strength buffers. This extraction procedure s eparated acid pyrophosphatase activity into three parts. One of these activities appears to correspond to the purple phosphatase isolated by other workers (1-3). The other two fractions showed both general phos phomonoesterase and pyrophosphatase activity, but were most active wit h pyrophosphate and were used for further characterization. The pH opt imum for the enzyme was approx 5.5-6.0 with pyrophosphatase, and it ex hibited substrate inhibition with pyrophosphate and ATP at low pH. The partially purified acid pyrophosphatase was estimated to be a dimer o f approx 98 kDa (mol wt estimated by gel filtration on Sephacryl S-200 ) with no detectable carbohydrate or iron content. Of the cations test ed for their effect on pyrophosphatase activity, iron was the most inh ibitory, followed by magnesium and zinc.