1. Oxidoreductases

 2. Transferases

 3. Hydrolases

 4. Lyases

 5. Isomerases

   5.1  Racemases and epimerases

   5.2  cis-trans-Isomerases

   5.3  Intramolecular oxidoreductases

     5.3.1  Interconverting aldoses and ketoses, and related compounds

     5.3.2  Interconverting keto- and enol-groups

       5.3.2.1  phenylpyruvate tautomerase

       5.3.2.2  oxaloacetate tautomerase

       5.3.2.3  TDP-4-oxo-6-deoxy-alpha-D-glucose-3,4-oxoisomerase (dTDP-3-dehydro-6-deoxy-alpha-D-galactopyranose-forming)

       5.3.2.4  TDP-4-oxo-6-deoxy-alpha-D-glucose-3,4-oxoisomerase (dTDP-3-dehydro-6-deoxy-alpha-D-glucopyranose-forming)

       5.3.2.5  2,3-diketo-5-methylthiopentyl-1-phosphate enolase

       5.3.2.6  2-hydroxymuconate tautomerase

       5.3.2.7  ascopyrone tautomerase

       5.3.2.8  4-oxalomesaconate tautomerase

     5.3.3  Transposing C=C bonds

     5.3.4  Transposing S-S bonds

     5.3.99  Other intramolecular oxidoreductases

   5.4  Intramolecular transferases

   5.5  Intramolecular lyases

   5.6  Isomerases altering macromolecular conformation

   5.99  Other isomerases

 6. Ligases

 7. Translocases