Properties of Poly(ADP-ribose) Glycohydrolase Purified from Pig Testis Nuclei

A poly(ADP-ribose) glycohydrolase was purified more than 5,000-fold to apparent homogeneity from pig testis nuclei with a yield of 16%. A protein band, whose molecular mass (Mr) was estimated to be 58,000, detected by SDS–polyacrylamide gel electrophoresis of the purified preparation, was shown to have glycohydrolase activity upon assay by the renaturation method. A nativeMrof 51,000 was determined by gel permeation. This polypeptide is a basic protein with a pIvalue of 8.8. The mode of hydrolysis of poly(ADP-ribose) [(ADP-ribose)n] by this enzyme is exoglycosidic, yielding ADP-ribose as the final product. TheKmvalue for (ADP-ribose)n(average chain length,n= 15) is 5.4 μMand theVmaxof its hydrolysis is 34.5 μmol· min−1·mg protein−1. The optimum pH for enzyme activity is 7.2. Low concentrations (50 ∼ 150 mM) of monovalent salts stimulate the enzyme activity. The poly- (ADP-ribose) glycohydrolase present in pig testis nuclei has some properties different from either nuclear poly(ADP-ribose) glycohydrolase (type I) or cytoplasmic poly(ADP-ribose) glycohydrolase (type II), purified previously from several tissues including pig thymus, guinea pig liver, calf thymus, human erythrocytes, and placenta. These differences suggest the tissue specificity of poly(ADP-ribose) glycohydrolase.