Conventional opinion about enzyme regulation is allosteric regulation which was established on the basis of protein three dimensional structure theory. New view about it is thermodynamic model for enzyme regulation. On the basis of thermodynamic model of enzyme regulation, we have classified all enzyme regulators into two groups: the first group refers to allodynamic regulator which adjusts global conformation of an enzyme and influences thermal equilibrium between inactive and active conformation of the enzyme. Second group refers to local modulator which adjust local conformation at active site of the enzyme. Drug interaction within a protein can be analyzed by this classification.