Studies on Two Nucleases and a Ribonuclease from Physarum polycephalum Purification and Mode of Action

Abstract

1. Two nucleases hydrolyzing both RNA and denatured DNA (Nucleases P_p−1 and P_p−1) and one ribonuclease (RNase P_p−4) were isolated from Physarum polycephalum in addition to the three RNases (RNases P_p−1, P_p−2 and P_p−3) reported in the preceding paper (1). 2. They are thermolabile. 3. The pH optima of nucleases P_p−1 and P_p−2 are pH4.5, and that of RNase P_p−4 is pH4.0. 4. Nuclease P_pv1 and nuclease P_p−2 hydrolyze denatured DNA as well as RNA, but not native DNA. 5. Nuclease P_p−1 hydrolyzes RNA forming nucleotides with terminal 3'-phosphate. 6. Nuclease P_p−2 hydrolyzes RNA to produce nucleotides with terminal 5'-phosphate. It has no base specificity. 7. RNase P_p−4 hydrolyzes RNA forming nucleotides bearing 5'-phosphate group with purine preference in regards to 3'-terminal nucleotides. 8. Nuclease P_p−2 and RNase P_p−4 are strongly activated by Zn⁺⁺.