Enzymatic Catalysis

The speeding up of a process through the use of an "enzyme" is known as enzyme catalysis. The majority of these processes—chemical reactions—involve proteins, which make up most enzymes. The active site is a specific location where catalysis often takes place within an enzyme. Proteins make up the majority of enzymes; these proteins may be found in a single protein chain or several chains together in a multi-subunit complex. Frequently, non-protein components like metal ions or specialised chemical molecules known as cofactors are also incorporated by enzymes (e.g. adenosine triphosphate). Many cofactors are vitamins, and their employment in the catalysis of biological processes within metabolism is intimately related to their function as vitamins. Many, but not all, metabolically necessary processes have very low catalytic enthalpies, hence it is crucial that the cell can efficiently catalyse biological reactions. Although only the most important enzymes operate near catalytic efficiency limitations and many enzymes are far from optimum, the optimization of such catalytic activity is a major force in protein evolution. In addition to conventional acid and base catalysis, orbital steering, entropic restriction, orientation effects (also known as lock and key catalysis), motional effects involving protein dynamics, and entropic effects are also significant variables in enzyme catalysis. Although enzyme catalysis mechanisms differ, they are all, in theory, comparable to other forms of chemical catalysis in that lowering the energy barrier(s) separating the reactants from the products—or substrates—is essential. The percentage of reactant molecules that can break through this barrier and produce the product increases when activation energy (Ea) is reduced.