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

 4. Lyases

 5. Isomerases

 6. Ligases

   6.1  Forming carbon-oxygen bonds

   6.2  Forming carbon-sulfur bonds

   6.3  Forming carbon-nitrogen bonds

   6.4  Forming carbon-carbon bonds

     6.4.1  Ligases that form carbon-carbon bonds (only sub-subclass identified to date)

       6.4.1.1  pyruvate carboxylase

       6.4.1.2  acetyl-CoA carboxylase

       6.4.1.3  propionyl-CoA carboxylase

       6.4.1.4  methylcrotonoyl-CoA carboxylase

       6.4.1.5  geranoyl-CoA carboxylase

       6.4.1.6  acetone carboxylase

       6.4.1.7  2-oxoglutarate carboxylase

       6.4.1.8  acetophenone carboxylase

       6.4.1.9  coenzyme F430 synthetase

   6.5  Forming phosphoric-ester bonds

   6.6  Forming nitrogen-metal bonds

   6.7  Forming nitrogen-nitrogen bonds

 7. Translocases