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Table 1 Distribution of non-homologous isofunctional enzymes among enzyme classes

From: Non-homologous isofunctional enzymes: A systematic analysis of alternative solutions in enzyme evolution

Enzyme class Enzyme nodes in ENZYMEa Enzyme nodes in KEGGa Sequences with EC numbers EC nodes with analogous enzymes Fraction of the EC nodes
     Two classes of enzymes Three or more classes  
Oxidoreductases (EC 1) 1343 (625) 575 98,166 31 5 5.8%
Transferases (EC 2) 1296 (683) 625 150,596 24 2 3.8%
Hydrolases (EC 3)c 930c (441) 427c 81,538 76 11 19.7%d
Lyases (EC 4) 469 (235) 210 45,074 15 3 7.7%
Isomerases (EC 5) 177 (106) 100 30,429 15 2 16.0%e
Ligases (EC 6) 148(97) 104 44,829 1 0 1.0%
Total 4,363 (2,187) 2,041 450,632 185 4.4%
  1. a - Only the EC nodes containing all 4 digits were considered; the numbers of EC nodes with at least one assigned protein sequence are shown in parentheses
  2. b - From the in KEGG database, based on a set of 718 complete genomes
  3. c - Peptidases (EC 3.4.x.x) were excluded from the analyzed set
  4. d - EC nodes with analogous enzymes are overrepresented (p < 1 × 10-12)
  5. e - Overrepresentation of EC nodes with analogous enzymes is not statistically significant (p ~ 0.08).