_EC 3.4.21.- Serine endopeptidases. 5,009 PDB entries  
EC 3.-.-.- Hydrolases. [52,127 PDB entries]
EC 3.4.-.- Acting on peptide bonds (peptidases). [15,978 PDB entries]
EC 3.4.21.- Serine endopeptidases. [5,009 PDB entries]
EC 3.4.21.1 chymotrypsin. [94 PDB entries]
EC 3.4.21.2 chymotrypsin C. [2 PDB entries]
EC 3.4.21.3 metridin. [-]
EC 3.4.21.4 trypsin. [759 PDB entries]
EC 3.4.21.5 thrombin. [504 PDB entries]
EC 3.4.21.6 coagulation factor Xa. [177 PDB entries]
EC 3.4.21.7 plasmin. [47 PDB entries]
EC 3.4.21.8 Transferred entry: 3.4.21.34 and 3.4.21.35. [-]
EC 3.4.21.9 enteropeptidase. [15 PDB entries]
EC 3.4.21.10 acrosin. [2 PDB entries]
EC 3.4.21.11 Transferred entry: 3.4.21.36 and 3.4.21.37. [-]
EC 3.4.21.12 alpha-lytic endopeptidase. [49 PDB entries]
EC 3.4.21.13 Transferred entry: 3.4.16.5 and 3.4.16.6. [-]
EC 3.4.21.14 Transferred entry: 3.4.21.62, 3.4.21.63, 3.4.21.64, 3.4.21.65 and [4 PDB entries]
EC 3.4.21.15 Transferred entry: 3.4.21.63. [-]
EC 3.4.21.16 Deleted entry. [-]
EC 3.4.21.17 Deleted entry. [-]
EC 3.4.21.18 Deleted entry. [-]
EC 3.4.21.19 glutamyl endopeptidase. [11 PDB entries]
EC 3.4.21.20 cathepsin G. [13 PDB entries]
EC 3.4.21.21 coagulation factor VIIa. [116 PDB entries]
EC 3.4.21.22 coagulation factor IXa. [53 PDB entries]
EC 3.4.21.23 Deleted entry. [-]
EC 3.4.21.24 Deleted entry. [-]
EC 3.4.21.25 cucumisin. [2 PDB entries]
EC 3.4.21.26 prolyl oligopeptidase. [69 PDB entries]
EC 3.4.21.27 coagulation factor XIa. [109 PDB entries]
EC 3.4.21.28 Transferred entry: 3.4.21.74. [-]
EC 3.4.21.29 Transferred entry: 3.4.21.74. [-]
EC 3.4.21.30 Transferred entry: 3.4.21.74. [-]
EC 3.4.21.31 Transferred entry: 3.4.21.68 and 3.4.21.73. [-]
EC 3.4.21.32 brachyurin. [1 PDB entries]
EC 3.4.21.33 Deleted entry. [-]
EC 3.4.21.34 plasma kallikrein. [19 PDB entries]
EC 3.4.21.35 tissue kallikrein. [10 PDB entries]
EC 3.4.21.36 pancreatic elastase. [128 PDB entries]
EC 3.4.21.37 leukocyte elastase. [36 PDB entries]
EC 3.4.21.38 coagulation factor XIIa. [17 PDB entries]
EC 3.4.21.39 chymase. [20 PDB entries]
EC 3.4.21.40 Deleted entry. [-]
EC 3.4.21.41 complement subcomponent C1r. [12 PDB entries]
EC 3.4.21.42 complement subcomponent C1s. [13 PDB entries]
EC 3.4.21.43 classical-complement-pathway C3/C5 convertase. [8 PDB entries]
EC 3.4.21.44 Transferred entry: 3.4.21.43. [-]
EC 3.4.21.45 complement factor I. [2 PDB entries]
EC 3.4.21.46 complement factor D. [42 PDB entries]
EC 3.4.21.47 alternative-complement-pathway C3/C5 convertase. [26 PDB entries]
EC 3.4.21.48 cerevisin. [-]
EC 3.4.21.49 hypodermin C. [2 PDB entries]
EC 3.4.21.50 lysyl endopeptidase. [5 PDB entries]
EC 3.4.21.51 Deleted entry. [-]
EC 3.4.21.52 Deleted entry. [-]
EC 3.4.21.53 endopeptidase La. [96 PDB entries]
EC 3.4.21.54 gamma-renin. [-]
EC 3.4.21.55 venombin Ab. [-]
EC 3.4.21.56 Deleted entry. [-]
EC 3.4.21.57 leucyl endopeptidase. [-]
EC 3.4.21.58 Deleted entry. [-]
EC 3.4.21.59 tryptase. [32 PDB entries]
EC 3.4.21.60 scutelarin. [-]
EC 3.4.21.61 kexin. [3 PDB entries]
EC 3.4.21.62 subtilisin. [140 PDB entries]
EC 3.4.21.63 oryzin. [4 PDB entries]
EC 3.4.21.64 peptidase K. [258 PDB entries]
EC 3.4.21.65 thermomycolin. [-]
EC 3.4.21.66 thermitase. [4 PDB entries]
EC 3.4.21.67 endopeptidase So. [-]
EC 3.4.21.68 t-plasminogen activator. [12 PDB entries]
EC 3.4.21.69 activated protein C (thrombin-activated peptidase). [10 PDB entries]
EC 3.4.21.70 pancreatic endopeptidase E. [-]
EC 3.4.21.71 pancreatic elastase Ii. [1 PDB entries]
EC 3.4.21.72 IgA-specific serine endopeptidase. [1 PDB entries]
EC 3.4.21.73 u-plasminogen activator. [164 PDB entries]
EC 3.4.21.74 venombin A. [-]
EC 3.4.21.75 furin. [43 PDB entries]
EC 3.4.21.76 myeloblastin. [1 PDB entries]
EC 3.4.21.77 semenogelase. [4 PDB entries]
EC 3.4.21.78 granzyme A. [2 PDB entries]
EC 3.4.21.79 granzyme B. [3 PDB entries]
EC 3.4.21.80 streptogrisin A. [5 PDB entries]
EC 3.4.21.81 streptogrisin B. [28 PDB entries]
EC 3.4.21.82 glutamyl endopeptidase Ii. [1 PDB entries]
EC 3.4.21.83 oligopeptidase B. [2 PDB entries]
EC 3.4.21.84 limulus clotting factor C. [-]
EC 3.4.21.85 limulus clotting factor B. [-]
EC 3.4.21.86 limulus clotting enzyme. [-]
EC 3.4.21.87 Transferred entry: 3.4.23.49. [-]
EC 3.4.21.88 repressor LexA. [18 PDB entries]
EC 3.4.21.89 signal peptidase I. [17 PDB entries]
EC 3.4.21.90 togavirin. [142 PDB entries]
EC 3.4.21.91 flavivirin. [678 PDB entries]
EC 3.4.21.92 endopeptidase Clp. [178 PDB entries]
EC 3.4.21.93 proprotein convertase 1. [6 PDB entries]
EC 3.4.21.94 proprotein convertase 2. [-]
EC 3.4.21.95 snake venom factor V activator. [4 PDB entries]
EC 3.4.21.96 lactocepin. [-]
EC 3.4.21.97 assemblin. [38 PDB entries]
EC 3.4.21.98 hepacivirin. [423 PDB entries]
EC 3.4.21.99 spermosin. [-]
EC 3.4.21.100 sedolisin. [9 PDB entries]
EC 3.4.21.101 xanthomonalisin. [-]
EC 3.4.21.102 C-terminal processing peptidase. [16 PDB entries]
EC 3.4.21.103 physarolisin. [-]
EC 3.4.21.104 mannan-binding lectin-associated serine protease-2. [10 PDB entries]
EC 3.4.21.105 rhomboid protease. [53 PDB entries]
EC 3.4.21.106 hepsin. [6 PDB entries]
EC 3.4.21.107 peptidase Do. [79 PDB entries]
EC 3.4.21.108 HtrA2 peptidase. [12 PDB entries]
EC 3.4.21.109 matriptase. [25 PDB entries]
EC 3.4.21.110 C5a peptidase. [6 PDB entries]
EC 3.4.21.111 aqualysin 1. [1 PDB entries]
EC 3.4.21.112 site-1 protease. [2 PDB entries]
EC 3.4.21.113 pestivirus NS3 polyprotein peptidase. [44 PDB entries]
EC 3.4.21.114 equine arterivirus serine peptidase. [-]
EC 3.4.21.115 infectious pancreatic necrosis birnavirus Vp4 peptidase. [1 PDB entries]
EC 3.4.21.116 SpoIVB peptidase. [1 PDB entries]
EC 3.4.21.117 stratum corneum chymotryptic enzyme. [15 PDB entries]
EC 3.4.21.118 kallikrein 8. [3 PDB entries]
EC 3.4.21.119 kallikrein 13. [1 PDB entries]
EC 3.4.21.120 oviductin. [-]
EC 3.4.21.121 Lys-Lys/Arg-Xaa endopeptidase. [2 PDB entries]
EC 3.4.21.122 transmembrane protease serine 2. [31 PDB entries]
EC 3.4.21.123 kumamolysin. [7 PDB entries]

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