A catalyst is a chemical involved in, but not changed by, a chemical reaction. Many enzymes function by lowering the activation energy of reactions. By bringing the reactants closer together, chemical bonds may be weakened and reactions will proceed faster than without the catalyst. Carbonic anhydrase speeds up the transfer of carbon dioxide from cells to the blood. There are over 2000 known enzymes, each of which is involved with one specific chemical reaction.
Enzymes are substrate specific.
Difference between a catalyzed and uncatalyzed reaction. Note that the catalyzed reaction occurs at a lower activation energy than the uncatalyzed reaction. Enzymes are proteins. The functioning of the enzyme is determined by the shape of the protein. It recognizes, confines and orients the substrate in a particular direction.