The Endonuclease catalyzes the hydrolysis of both DNA and RNA， double or single stranded， at position 3’ of the phosphodiester bond to generate 5’-phosphorylated mono-， di-， tri- and tetranucleotides（DNA being the slightly better substrate than RNA). Endonuclease binds one magnesium ion as cofactor. Endonuclease active site contains one hydrated magnesium ion which has only one direct interaction with the protein， while all the other interactions are via water molecules.
