_EC 3.1.31.- Endoribonucleases active with either ribo- or deoxyribonucleic ac 230 PDB entries  
EC 3.-.-.- Hydrolases. [21,051 PDB entries]
EC 3.1.-.- Acting on ester bonds. [5,973 PDB entries]
EC 3.1.31.- Endoribonucleases active with either ribo- or deoxyribonucleic ac [230 PDB entries]    
EC 3.1.31.1 Micrococcal nuclease. [230 PDB entries]