1. Oxidoreductases

 2. Transferases

   2.1  Transferring one-carbon groups

     2.1.1  Methyltransferases

     2.1.2  Hydroxymethyl-, formyl- and related transferases

     2.1.3  Carboxy- and carbamoyltransferases

       2.1.3.1  methylmalonyl-CoA carboxytransferase

       2.1.3.2  aspartate carbamoyltransferase

       2.1.3.3  ornithine carbamoyltransferase

       2.1.3.5  oxamate carbamoyltransferase

       2.1.3.6  putrescine carbamoyltransferase

       2.1.3.7  3-hydroxymethylcephem carbamoyltransferase

       2.1.3.8  lysine carbamoyltransferase

       2.1.3.9  N-acetylornithine carbamoyltransferase

       2.1.3.10  malonyl-S-ACP:biotin-protein carboxyltransferase

       2.1.3.11  N-succinylornithine carbamoyltransferase

       2.1.3.12  decarbamoylnovobiocin carbamoyltransferase

       2.1.3.15  acetyl-CoA carboxytransferase

       2.1.3.16  ureidoglycine carbamoyltransferase

     2.1.4  Amidinotransferases

     2.1.5  Methylenetransferases

   2.2  Transferring aldehyde or ketonic groups

   2.3  Acyltransferases

   2.4  Glycosyltransferases

   2.5  Transferring alkyl or aryl groups, other than methyl groups

   2.6  Transferring nitrogenous groups

   2.7  Transferring phosphorus-containing groups

   2.8  Transferring sulfur-containing groups

   2.9  Transferring selenium-containing groups

   2.10  Transferring molybdenum- or tungsten-containing groups

 3. Hydrolases

   3.1  Acting on ester bonds

   3.2  Glycosylases

   3.3  Acting on ether bonds

   3.4  Acting on peptide bonds (peptidases)

   3.5  Acting on carbon-nitrogen bonds, other than peptide bonds

     3.5.1  In linear amides

     3.5.2  In cyclic amides

       3.5.2.1  barbiturase

       3.5.2.2  dihydropyrimidinase

       3.5.2.3  dihydroorotase

       3.5.2.4  carboxymethylhydantoinase

       3.5.2.5  allantoinase

       3.5.2.6  beta-lactamase

       3.5.2.7  imidazolonepropionase

       3.5.2.9  5-oxoprolinase (ATP-hydrolysing)

       3.5.2.10  creatininase

       3.5.2.11  L-lysine-lactamase

       3.5.2.12  6-aminohexanoate-cyclic-dimer hydrolase

       3.5.2.13  2,5-dioxopiperazine hydrolase

       3.5.2.14  N-methylhydantoinase (ATP-hydrolysing)

       3.5.2.15  cyanuric acid amidohydrolase

       3.5.2.16  maleimide hydrolase

       3.5.2.17  hydroxyisourate hydrolase

       3.5.2.18  enamidase

       3.5.2.19  streptothricin hydrolase

       3.5.2.20  isatin hydrolase

     3.5.3  In linear amidines

     3.5.4  In cyclic amidines

     3.5.5  In nitriles

     3.5.99  In other compounds

   3.6  Acting on acid anhydrides

   3.7  Acting on carbon-carbon bonds

   3.8  Acting on halide bonds

   3.9  Acting on phosphorus-nitrogen bonds

   3.10  Acting on sulfur-nitrogen bonds

   3.11  Acting on carbon-phosphorus bonds

   3.12  Acting on sulfur-sulfur bonds

   3.13  Acting on carbon-sulfur bonds

 4. Lyases

 5. Isomerases

 6. Ligases

   6.1  Forming carbon-oxygen bonds

   6.2  Forming carbon-sulfur bonds

   6.3  Forming carbon-nitrogen bonds

     6.3.1  Acid-D-ammonia (or amine) ligases (amide synthases)

     6.3.2  Acid-D-amino-acid ligases (peptide synthases)

     6.3.3  Cyclo-ligases

     6.3.4  Other carbon-nitrogen ligases

     6.3.5  Carbon-nitrogen ligases with glutamine as amido-N-donor

       6.3.5.1  NAD+ synthase (glutamine-hydrolysing)

       6.3.5.2  GMP synthase (glutamine-hydrolysing)

       6.3.5.3  phosphoribosylformylglycinamidine synthase

       6.3.5.4  asparagine synthase (glutamine-hydrolysing)

       6.3.5.5  carbamoyl-phosphate synthase (glutamine-hydrolysing)

       6.3.5.6  asparaginyl-tRNA synthase (glutamine-hydrolysing)

       6.3.5.7  glutaminyl-tRNA synthase (glutamine-hydrolysing)

       6.3.5.9  hydrogenobyrinic acid a,c-diamide synthase (glutamine-hydrolysing)

       6.3.5.10  adenosylcobyric acid synthase (glutamine-hydrolysing)

       6.3.5.11  cobyrinate a,c-diamide synthase

       6.3.5.12  Ni-sirohydrochlorin a,c-diamide synthase

       6.3.5.13  lipid II isoglutaminyl synthase (glutamine-hydrolysing)

   6.4  Forming carbon-carbon bonds

   6.5  Forming phosphoric-ester bonds

   6.6  Forming nitrogen-metal bonds

   6.7  Forming nitrogen-nitrogen bonds

 7. Translocases