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4.5.6. Nomenclature and classification of enzymes

Nomenclature and classification of enzymes

To name an enzyme, first the name of the substrate is named, then the name of the coenzyme, if any, and finally the function that the enzyme performs. For example, malonate coenzyme A-transferasecytochrome oxidasesuccinate flavin dehydrogenase, etc. Usually the name of the substrate finished in -ase is used, for example: sucrasemaltaseamylase, and so on. Some enzymes, however, retain their old names, such as trypsinpepsin, etc.

According to the type of reaction that enzymes catalyze, they are classified into six groups:

  1. Oxidoreductases. They catalyze reactions in which an oxidation or reduction of the substrate takes place. They are enzymes of the respiratory chain. They are dehydrogenasesoxidasesperoxidasesoxygenases or reductases.
  2. Transferases. They transfer radicals or functional groups from one substrate to another.
  3. Hydrolases. They act through hydrolysis reactions , breaking bonds by introducing the –OH and –H radicals from the breakdown of a water molecule.
  4. Liases. They catalyze reactions in which C–C, C–N or C–O bonds are broken, with loss of groups and, generally, with the appearance of double bonds.
  5. Isomerases. They are enzymes that catalyze isomerization reactions, in which the substrate is transformed into another isomeric molecule.
  6. Ligases or synthetases. They bind molecules or radicals through the energy provided by the dephosphorylation of an ATP molecule .


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