Enzymes are molecules of a protein and structural nature which catalyse chemical reactions if they are thermodynamically possible: an enzyme makes a chemical reaction that is energetically possible (see Gibbs Free Energy) but that proceeds at a very low speed become kinetically favourable, i.e., making it proceed faster than in the absence of the enzyme.
In these reactions, enzymes act on molecules called substrates, which are converted into different molecules called products. Almost all processes in cells need enzymes to occur at significant rates. Enzyme-mediated reactions are called enzymatic reactions.
Since enzymes are highly selective for their substrates and their speed increases in only some reactions, the set of synthesized enzymes in a cell determines the type of metabolism each cell will have. In turn, this synthesis depends on the regulation of gene expression.
Like all catalysts, enzymes work by decreasing the activation energy (ΔG ‡) for a reaction so that the reaction rate is substantially accelerated. Enzymes do not alter the energy balance of the reactions in which they are involved consequently they do not modify the balance of the reaction but manage to speed up the process even millions of times. A reaction controlled by of an enzyme or any catalyst reaches equilibrium much faster than the corresponding uncatalyzed reaction
As with other catalysts, enzymes are not consumed by the reactions they catalyze, nor do they alter their chemical balance. However, they differ from other catalysts for they are more specific. Enzymes catalyze about 4,000 different biochemical reactions. Not all proteins are biochemical catalysts for some RNA molecules are capable of catalyzing reactions (such as the 16S ribosomes subunit in which peptidyl transferase activity resides). It is also worth naming the synthetic molecules called artificial enzymes capable of catalyzing chemical reactions as classical enzymes.
Enzymatic activity can be affected by other molecules. Enzymatic inhibitors are molecules that decrease enzymatic activity, while activators are molecules that increase this activity. Moreover, many enzymes require cofactors to work. Many drugs are molecule inhibitors. Similarly, the activity is affected by temperature, pH, the concentration of the enzyme itself and that of the substrate, and by other physicochemical factors.
Some enzymes are commercially used, for example, in the synthesis of antibiotics and other pharmaceuticals, such as Brix 3000 and other innovative and revolutionary products that Brix Medical Science is developing to launch shortly.