Oxidoreductases (EC 1)
Transferases (EC 2)
Hydrolases (EC 3)
Lyases (EC 4)
Isomerases (EC 5)
Ligases (EC 6)
However, it has become apparent that none of these could describe the important group of enzymes that catalyse the movement of ions or molecules across membranes or their separation within membranes. Several of these involve the hydrolysis of ATP and had been previously classified as ATPases (EC 3.6.3.-), although the hydrolytic reaction is not their primary function.
These enzymes have now been classified under a new EC class of Translocases (EC 7). The reactions catalyzed are designated as transfers from ‘side 1’ to ‘side 2’ because the designations ‘in’ and ‘out’ (or ‘cis’ and ‘trans’), which had been used previously, lack clarity and can be ambiguous. The comments associated with each entry then describe the specific translocations catalysed.
The subclasses designate the types of ion or molecule translocated:
- EC 7.1 contains enzymes catalysing the translocation of hydrons (hydron being the general name for H+ in its natural abundance),
- EC 7.2 contains those catalysing the translocation of inorganic cations and their chelates,
- EC 7.3 contains those catalysing the translocation of inorganic anions,
- EC 7.4 contains those catalysing the translocation of amino acids and peptides,
- EC 7.5 contains those catalysing the translocation of carbohydrates and their derivatives
- EC 7.6 contains those catalysing the translocation of other compounds.
- EC 7.x.1 translocations linked to oxidoreductase reactions
- EC 7.x.2 translocations linked to the hydrolysis of a nucleoside triphosphate
- EC 7.x.3 translocations linked to the hydrolysis of a diphosphate
- EC 7.x.4 translocations linked to a decarboxylation reaction
(prepared by Keith Tipton, originally published at the ExplorEnz enzyme database)