_EC 3.1.21.- Endodeoxyribonucleases producing 5'-phosphomonoesters. 140 PDB entries  
EC 3.-.-.- Hydrolases. [19,780 PDB entries]
EC 3.1.-.- Acting on ester bonds. [5,755 PDB entries]
EC 3.1.21.- Endodeoxyribonucleases producing 5'-phosphomonoesters. [140 PDB entries]    
EC 3.1.21.1 Deoxyribonuclease I. [14 PDB entries]
EC 3.1.21.2 Deoxyribonuclease Iv. [16 PDB entries]
EC 3.1.21.3 Type I site-specific deoxyribonuclease. [5 PDB entries]
EC 3.1.21.4 Type Ii site-specific deoxyribonuclease. [99 PDB entries]
EC 3.1.21.5 Type Iii site-specific deoxyribonuclease. [-]
EC 3.1.21.6 CC-preferring endodeoxyribonuclease. [-]
EC 3.1.21.7 Deoxyribonuclease V. [6 PDB entries]
EC 3.1.21.8 T(4) deoxyribonuclease Ii. [-]
EC 3.1.21.9 T(4) deoxyribonuclease Iv. [-]

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