An active site is a specific part of an enzyme formed by several amino acids that are directly involved in the catalysis. Active site binds substrate and catalyzes the reaction resulting in the production of a particular product. Allosteric site is a specific part of an enzyme formed by several amino acids that provide the modulation of enzymatic activity. Allosteric site binds a particular ligand that influences the rate of catalysis of the enzyme. This allosteric regulator may decrease (inhibit) or increase (activate) the enzyme altering the catalysis rate.