An enzyme is a biological catalyst. Enzymes accelerate chemical reactions in living cells and tissues. All enzymes are proteins, although some RNA molecules can act as enzymes (ribozymes).
Most enzymes are named after the substrate that they act upon. For example, lactase is the enzyme that cleaves the sugar lactose into glucose and galactose, while DNA polymerase catalyzes the formation of new DNA strands from nucleotides. The suffix “-ase” is used to denote an enzyme.
Enzymes are classified into six broad categories: oxidoreductases, transferases, hydrolases, lyases, isomerases, and ligases.
Oxidoreductases catalyze oxidation-reduction reactions. These reactions involve the transfer of electrons between molecules. examples of oxidoreductases include dehydrogenases, which remove hydrogen atoms from a molecule; oxygenases, which add oxygen atoms to a molecule; and peroxidases, which transfer hydrogen atoms between molecules.
Transferases catalyze the transfer of functional groups from one molecule to another. examples of transferases include kinases, which phosphorylate proteins; glycosyltransferases, which add sugars to proteins; and acetyltransferases, which add acetyl groups to proteins.
Hydrola