noun, plural: lyases
An enzyme is a catalyst or a chemical produced by cells to speed up a biochemical reaction. It is usually a protein molecule with a characteristic sequence of amino acids that fold to produce a specific three-dimensional structure, which gives the molecule unique properties. Other molecule with catalytic activity is ribozyme, an enzyme made of RNA rather than protein. Enzymes may be classified and named according to the reaction they catalyze: (1) oxidoreductases, (2) transferases, (3) lyases, (4) isomerases, and (6) ligases.
Lyases are enzymes that catalyze the breaking a chemical bond between two parts of a molecule through biochemical means other than hydrolysis and oxidation. They often form a double bond or add a new ring structure. An example is the lyase that acts on ATP resulting in the formation of cAMP and PPi.
One of the distinctive characteristics of a lyase is requiring one substrate for the reaction in one direction and two substrates for the reverse reaction (referred to as Michael addition).
Lyases include decarboxylases, aldolases and dehydratases.