Nuclease P1 gene (nuc P1)which was cloned from Penicillium citrinum and expressed in A percent niger Bdel4 with the low-background extracellular protein percent The expression strategy of multi-copy nuc P1 in the A percent niger with the linker of 2A peptide was applied to improve the enzyme activity of nuclease P1, the highest activity up to 77 percent6 U/mL percent After Ni-chelate purification, the specific enzyme activity, the optimum temperature and pH were 32 percent4 U/mg, 65 °C and 5 percent3 respectively percent The recombination nuclease P1 was activated by addition of Mg2+, Zn2+ and Cu2+, and inhibited by addition of Ca2+, Fe2+, Mn2+, Ni2+, Co2+, Mg2+, K+ and EDTA percent Furthermore, the enzyme hydrolyses yeast RNA efficiently into 5'- nucleotides percent Through enzymolysis, the highest concentration of nucleotides achieved 15 percent12 mg/mL, and 75U nuclease P1 is suitable amount should be added to the enzymolysis system percent