_EC 3.1.-.- Acting on ester bonds. 12,883 PDB entries  
EC 3.-.-.- Hydrolases. [51,972 PDB entries]
EC 3.1.-.- Acting on ester bonds. [12,883 PDB entries]
EC 3.1.1.- Carboxylic ester hydrolases. [2,185 PDB entries]
EC 3.1.2.- Thiolester hydrolases. [352 PDB entries]
EC 3.1.3.- Phosphoric monoester hydrolases. [3,591 PDB entries]
EC 3.1.4.- Phosphoric diester hydrolases. [1,581 PDB entries]
EC 3.1.5.- Triphosphoric monoester hydrolases. [16 PDB entries]
EC 3.1.6.- Sulfuric ester hydrolases. [42 PDB entries]
EC 3.1.7.- Diphosphoric monoester hydrolases. [12 PDB entries]
EC 3.1.8.- Phosphoric triester hydrolases. [136 PDB entries]
EC 3.1.11.- Exodeoxyribonucleases producing 5'-phosphomonoesters. [233 PDB entries]
EC 3.1.12.- Exodeoxyribonucleases producing 3'-phosphomonoesters. [7 PDB entries]
EC 3.1.13.- Exoribonucleases producing 5'-phosphomonoesters. [1,716 PDB entries]
EC 3.1.14.- Exoribonucleases producing 3'-phosphomonoesters. [-]
EC 3.1.15.- Exonucleases active with either ribo- or deoxyribonucleic acids a [-]
EC 3.1.16.- Exonucleases active with either ribo- or deoxyribonucleic acids a [8 PDB entries]
EC 3.1.21.- Endodeoxyribonucleases producing 5'-phosphomonoesters. [273 PDB entries]
EC 3.1.22.- Endodeoxyribonucleases producing other than 5'-phosphomonoesters. [-]
EC 3.1.23.- Site specific endodeoxyribonucleases: cleavage is sequence specif [-]
EC 3.1.24.- Site specific endodeoxyribonucleases: cleavage is not sequence sp [-]
EC 3.1.25.- Site-specific endodeoxyribonucleases specific for altered bases. [-]
EC 3.1.26.- Endoribonucleases producing 5'-phosphomonoesters. [2,362 PDB entries]
EC 3.1.27.- Endoribonucleases producing other than 5'-phosphomonoesters. [7 PDB entries]
EC 3.1.30.- Endoribonucleases active with either ribo- or deoxyribonucleic ac [30 PDB entries]
EC 3.1.31.- Endoribonucleases active with either ribo- or deoxyribonucleic ac [332 PDB entries]

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