STUDIES ON ACID HYDROLASES .V. ISOLATION AND CHARACTERIZATION OF SPLEEN NUCLEOSIDE POLYPHOSPHATASE

1. 1. A new procedure is described for the purification of spleen nucleoside polyphosphatase, an enzyme able to split both the terminal phosphates of nucleoside tri-and di-phosphates and bis-(p-nitrophenyl) phosphate. The enzyme was eluted from the final CM-Sephadex column at a fairly constant specific activity. 2. 2. Using bis-(p-nitrophenyl) phosphate as the substrate, the enzyme showed a pH optimum close to 6.8, and a Michaelis constant equal to 0.95 mM. Phosphate ions are competitive inhibitors. The sedimentation constant of the enzyme was found to be equal to 3.2 S. 3. 3. A comparison of the hydrolytic activities on bis-(p-nitrophenyl) phosphate of 3 enzymes, acid deoxyribonuclease, spleen exonuclease, and nucleoside polyphosphatase, is presented. © 1968.