_EC 3.1.-.- Acting on ester bonds. 6,048 PDB entries  
EC 3.-.-.- Hydrolases. [21,435 PDB entries]
EC 3.1.-.- Acting on ester bonds. [6,048 PDB entries]    
EC 3.1.1.- Carboxylic ester hydrolases. [974 PDB entries]
EC 3.1.2.- Thiolester hydrolases. [79 PDB entries]
EC 3.1.3.- Phosphoric monoester hydrolases. [1,372 PDB entries]
EC 3.1.4.- Phosphoric diester hydrolases. [467 PDB entries]
EC 3.1.5.- Triphosphoric monoester hydrolases. [-]
EC 3.1.6.- Sulfuric ester hydrolases. [12 PDB entries]
EC 3.1.7.- Diphosphoric monoester hydrolases. [19 PDB entries]
EC 3.1.8.- Phosphoric triester hydrolases. [75 PDB entries]
EC 3.1.11.- Exodeoxyribonucleases producing 5'-phosphomonoesters. [50 PDB entries]
EC 3.1.12.- Exodeoxyribonucleases producing 3'-phosphomonoesters. [2 PDB entries]
EC 3.1.13.- Exoribonucleases producing 5'-phosphomonoesters. [945 PDB entries]
EC 3.1.14.- Exoribonucleases producing 3'-phosphomonoesters. [-]
EC 3.1.15.- Exonucleases active with either ribo- or deoxyribonucleic acid an [-]
EC 3.1.16.- Exonucleases active with either ribo- or deoxyribonucleic acid an [-]
EC 3.1.21.- Endodeoxyribonucleases producing 5'-phosphomonoesters. [141 PDB entries]
EC 3.1.22.- Endodeoxyribonucleases producing other than 5'-phosphomonoesters. [18 PDB entries]
EC 3.1.23.- (not defined) [-]
EC 3.1.24.- (not defined) [-]
EC 3.1.25.- Site-specific endodeoxyribonucleases specific for altered bases. [6 PDB entries]
EC 3.1.26.- Endoribonucleases producing 5'-phosphomonoesters. [1,222 PDB entries]
EC 3.1.27.- Endoribonucleases producing other than 5'-phosphomonoesters. [423 PDB entries]
EC 3.1.30.- Endoribonucleases active with either ribo- or deoxyribonucleic ac [11 PDB entries]
EC 3.1.31.- Endoribonucleases active with either ribo- or deoxyribonucleic ac [232 PDB entries]

[-] signifies that there are no PDB entries for the given enzyme subclass