What are the characteristics of an active site?

An active site on an enzyme has seven key characteristics: 

1. The active site comprises only a small part of the enzyme. The larger portion of the enzyme’s structure acts as a supporting scaffold, providing shape and stability to the active site structure.  
2. The shape of the active site is complementary to the substrate, which ensures that the binding will result in a proper fit. 
3. The active site contains special catalytic residues that actually bind to the substrate molecule and hold on to it while the chemical reaction occurs. This binding is reversible and occurs via non-covalent interactions such as hydrogen bonds, van der Waals forces, and hydrophobic interactions. 
4. The active site minimizes the likelihood that undesirable reactions will occur by placing the reactants in just the right orientation and proximity to each other. 
5. The active site reduces the energy of the transition state and stabilizes the structure. 
6. On binding with the substrate, the active site can undergo significant conformational changes. 
7. An active site creates a predominantly non-polar microenvironment. Water molecules are only found in an active site if and when water is a reactant in the reaction.