_EC 3.1.21.- Endodeoxyribonucleases producing 5'-phosphomonoesters. 273 PDB entries  
EC 3.-.-.- Hydrolases. [51,972 PDB entries]
EC 3.1.-.- Acting on ester bonds. [12,883 PDB entries]
EC 3.1.21.- Endodeoxyribonucleases producing 5'-phosphomonoesters. [273 PDB entries]
EC 3.1.21.1 deoxyribonuclease I. [49 PDB entries]
EC 3.1.21.2 deoxyribonuclease Iv. [22 PDB entries]
EC 3.1.21.3 type I site-specific deoxyribonuclease. [15 PDB entries]
EC 3.1.21.4 type Ii site-specific deoxyribonuclease. [145 PDB entries]
EC 3.1.21.5 type Iii site-specific deoxyribonuclease. [2 PDB entries]
EC 3.1.21.6 CC-preferring endodeoxyribonuclease. [-]
EC 3.1.21.7 deoxyribonuclease V. [9 PDB entries]
EC 3.1.21.8 T4 deoxyribonuclease Ii. [1 PDB entries]
EC 3.1.21.9 T4 deoxyribonuclease Iv. [-]
EC 3.1.21.10 crossover junction endodeoxyribonuclease. [30 PDB entries]

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