Enzyme Classes Reference

This single HTML file summarizes the official major enzyme classes by EC category and explains, in plain language, what each class does. It works offline and includes both a searchable table and mobile-friendly cards.

Single file Works offline Searchable EC classes 1-7
EC class Class name What it does Typical action Common subtypes Examples Example reaction
EC 1 Oxidoreductases Catalyze oxidation-reduction reactions by transferring electrons, hydrogen atoms, or oxygen atoms between molecules. They oxidize one substrate and reduce another, often using cofactors such as NAD+, NADP+, FAD, or oxygen. Dehydrogenases, oxidases, reductases, peroxidases, monooxygenases, dioxygenases Lactate dehydrogenase; cytochrome c oxidase; catalase Lactate dehydrogenase converts lactate to pyruvate while transferring reducing equivalents to NAD+.
EC 2 Transferases Transfer a functional group from one molecule to another. They move groups such as methyl, acyl, amino, glycosyl, or phosphoryl groups from a donor substrate onto an acceptor substrate. Kinases, aminotransferases, methyltransferases, acyltransferases, glycosyltransferases Hexokinase; alanine aminotransferase; DNA methyltransferase Hexokinase transfers a phosphoryl group from ATP to glucose to make glucose-6-phosphate.
EC 3 Hydrolases Break chemical bonds by hydrolysis, meaning by adding water. They cleave ester, peptide, glycosidic, phosphoric anhydride, or other bonds with water acting as a reactant. Proteases, phosphatases, lipases, nucleases, glycosidases Trypsin; alkaline phosphatase; lipase Trypsin hydrolyzes peptide bonds in proteins during digestion.
EC 4 Lyases Break or form bonds without hydrolysis or oxidation, often creating or removing double bonds. They cleave C-C, C-O, C-N, and related bonds by elimination, or add groups to double bonds in the reverse direction. Decarboxylases, aldolases, dehydratases, synthases Pyruvate decarboxylase; fumarase; aldolase Fumarase adds water across a double bond in fumarate to form malate, and can catalyze the reverse elimination reaction.
EC 5 Isomerases Rearrange atoms within a molecule to form an isomer. They catalyze intramolecular shifts, racemizations, epimerizations, cis-trans changes, or structural rearrangements without changing overall molecular formula. Racemases, epimerases, mutases, cis-trans isomerases Phosphoglucose isomerase; alanine racemase; phosphoglycerate mutase Phosphoglucose isomerase converts glucose-6-phosphate into fructose-6-phosphate.
EC 6 Ligases Join two molecules together, usually coupled to ATP or another nucleoside triphosphate. They form new bonds such as C-O, C-S, C-N, or C-C while using the energy of ATP cleavage or an equivalent energy source. Synthetases, carboxylases, DNA ligases DNA ligase; glutamine synthetase; pyruvate carboxylase DNA ligase seals breaks in DNA by joining adjacent nucleotides through phosphodiester bond formation.
EC 7 Translocases Catalyze the movement of ions or molecules across membranes or their separation within membranes. They couple transport to an energy source such as ATP hydrolysis, redox chemistry, or decarboxylation. ATP-driven pumps, electron-transport-linked pumps, ion pumps, protein translocases Na+/K+-ATPase; ATP synthase-related transport components; protein translocases Na+/K+-ATPase uses ATP hydrolysis to move sodium out of the cell and potassium into the cell.
EC 1

Oxidoreductases

What it does: Catalyze oxidation-reduction reactions by transferring electrons, hydrogen atoms, or oxygen atoms between molecules.

Typical action: They oxidize one substrate and reduce another, often using cofactors such as NAD+, NADP+, FAD, or oxygen.

Common subtypes: Dehydrogenases, oxidases, reductases, peroxidases, monooxygenases, dioxygenases

Examples: Lactate dehydrogenase; cytochrome c oxidase; catalase

Example reaction: Lactate dehydrogenase converts lactate to pyruvate while transferring reducing equivalents to NAD+.

EC 2

Transferases

What it does: Transfer a functional group from one molecule to another.

Typical action: They move groups such as methyl, acyl, amino, glycosyl, or phosphoryl groups from a donor substrate onto an acceptor substrate.

Common subtypes: Kinases, aminotransferases, methyltransferases, acyltransferases, glycosyltransferases

Examples: Hexokinase; alanine aminotransferase; DNA methyltransferase

Example reaction: Hexokinase transfers a phosphoryl group from ATP to glucose to make glucose-6-phosphate.

EC 3

Hydrolases

What it does: Break chemical bonds by hydrolysis, meaning by adding water.

Typical action: They cleave ester, peptide, glycosidic, phosphoric anhydride, or other bonds with water acting as a reactant.

Common subtypes: Proteases, phosphatases, lipases, nucleases, glycosidases

Examples: Trypsin; alkaline phosphatase; lipase

Example reaction: Trypsin hydrolyzes peptide bonds in proteins during digestion.

EC 4

Lyases

What it does: Break or form bonds without hydrolysis or oxidation, often creating or removing double bonds.

Typical action: They cleave C-C, C-O, C-N, and related bonds by elimination, or add groups to double bonds in the reverse direction.

Common subtypes: Decarboxylases, aldolases, dehydratases, synthases

Examples: Pyruvate decarboxylase; fumarase; aldolase

Example reaction: Fumarase adds water across a double bond in fumarate to form malate, and can catalyze the reverse elimination reaction.

EC 5

Isomerases

What it does: Rearrange atoms within a molecule to form an isomer.

Typical action: They catalyze intramolecular shifts, racemizations, epimerizations, cis-trans changes, or structural rearrangements without changing overall molecular formula.

Common subtypes: Racemases, epimerases, mutases, cis-trans isomerases

Examples: Phosphoglucose isomerase; alanine racemase; phosphoglycerate mutase

Example reaction: Phosphoglucose isomerase converts glucose-6-phosphate into fructose-6-phosphate.

EC 6

Ligases

What it does: Join two molecules together, usually coupled to ATP or another nucleoside triphosphate.

Typical action: They form new bonds such as C-O, C-S, C-N, or C-C while using the energy of ATP cleavage or an equivalent energy source.

Common subtypes: Synthetases, carboxylases, DNA ligases

Examples: DNA ligase; glutamine synthetase; pyruvate carboxylase

Example reaction: DNA ligase seals breaks in DNA by joining adjacent nucleotides through phosphodiester bond formation.

EC 7

Translocases

What it does: Catalyze the movement of ions or molecules across membranes or their separation within membranes.

Typical action: They couple transport to an energy source such as ATP hydrolysis, redox chemistry, or decarboxylation.

Common subtypes: ATP-driven pumps, electron-transport-linked pumps, ion pumps, protein translocases

Examples: Na+/K+-ATPase; ATP synthase-related transport components; protein translocases

Example reaction: Na+/K+-ATPase uses ATP hydrolysis to move sodium out of the cell and potassium into the cell.

Tip: search terms like “ATP”, “hydrolysis”, “oxidation”, “transport”, “kinase”, or “racemase” will filter the entries instantly.