Catalytic Mechanism

Category

Enzymes are divided into 7 groups based on the type of reactions catalyzed, which together with the identities of the substrates provide a basis for naming individual enzymes. It is also the basis for classification and code numbers.

Class 1. Oxidoreductases.

A_red + B_ox → Ao_x + B_red

This class, numbered under EC1, includes all enzymes catalyzing oxidoreduction reactions. The common name will be dehydrogenase and reductase. Oxidase is only used in cases where O₂ is the acceptor.
Oxidases: Use oxygen as an electron acceptor but do not incorporat it into substrate
Dehydrogenases: Use molecules other than oxygen (e.g., NAD⁺) as an electron acceptor
Oxygenases: Directly incorporate oxygen into the substrate
Peroxidases: Use H₂O₂ as an electron acceptor

Class 2. Transferases.

A - B + C → A + B - C

Transferases, numbered as EC2 are enzymes transferring a group to another compound (generally regarded as acceptor).
Methyltransferases: Transfer one-carbon units between substrates
Aminotransferases: Transfer NH₂ from amino acids to keto acids
Kinases: Transfer PO₃~ from ATP to a substrate
Phosphorylases: Transfer PO₃~from inorganic phosphate to a substrate

Class 3. Hydrolases.

A-B + H₂O → A-H + B-OH

EC3 hydrolases catalyze the hydrolytic cleavage of C-O, C-N, C-C and some other bonds, including phosphoric anhydride bonds. In most cases, the reaction with water as the acceptor was discovered earlier and is considered as the main physiological function of the enzyme, which is why these enzymes are classified as hydrolases rather than transferases.
Phosphatases: Remove PO_3- from a substrate
Phosphodiesterases: Cleave phosphodiester bonds such as those in nucleic acids
Proteases: Cleave amide bonds such as those in proteins

Class 4. Lyases.

A(XH)-B → A-X + B-H

EC4 enzymes cleave C-C, C-O, C-N, and other bonds by elimination, leaving double bonds or rings, or conversely adding groups to double bonds.
Decarboxylases: Produce CO₂ via elimination reactions
Aldolases: Produce aldehydes via elimination reactions
Synthases: Link two molecules without involvement of ATP

Class 5. Isomerases.

A-B → B-A

Isomerases are numbered as EC 5 and catalyze geometric or structural changes within one molecule. According to the type of isomerism, they may be called racemases, epimerases, cis-trans-isomerases, isomerases, tautomerases, mutases or cycloisomerases.
Racemases: Interconvert L and D stereoisomers
Mutases: Transfer groups between atoms within a molecule

Class 6. Ligases.

A + B + ATP → A-B + ADP + Pi

Ligases are enzymes catalyzing the joining together of two molecules coupled with the hydrolysis of a diphosphate bond in ATP or a similar triphosphate.
Carboxylases: Use CO₂ as a substrate
Synthetases: Link two molecules via an ATP-dependent reaction

Creative Enzymes provides numerous enzymes of all these different groups to its customers. Our excellent techniques guarantee high-quality products. We have manufacturing and development facilities run by specialized teams following the most up-to-date industrial standards.

Class 7. Translocases.

A new class EC 7, Translocases, has been added to the EC list. It will be part of ENZYME from release 2018_10. Read more about EC 7 here