1
oxidoreductases
Oxidation-reduction reaction (ex: lactate dehydrogenase)
2
transferases
group transfer (ex: nucleoside monophosphate kinase)
3
Hydrolases
hydrolysis reactions (transfer of functional groups to water) (ex: chymotrypsin)
4
Lyases
Addition or removal of groups to form double bonds (ex: fumarase)
5
Isomerases
isomerization (intramolecular group transfer) (ex: triose phosphate isomerase)
6
Ligases
ligation of two substrates at the expense of ATP hydrolysis (ex: aminoacyl-tRNA synthetase)