In
biochemistry, a
substrate is a
molecule upon which an
enzyme acts. Enzymes
catalyze chemical reactions involving the substrate(s). In the case of a single substrate, the substrate binds with the enzyme
active site, and an
enzyme-substrate complex is formed. The substrate is transformed into one or more
products, which are then released from the active site. The active site is now free to accept another substrate molecule. In enzymes with more than one substrate, these may bind in a particular order to the active site, before reacting together to produce products.
For example, in the reaction that occurs upon adding the enzyme rennin in milk, causing milk's coagulation, the substrate is milk and the enzyme is rennin. Another example is the reaction of the enzyme catalase in the decomposition of hydrogen peroxide. As an enzyme is a catalyst, it is not changed by the reactions it carries out.
A general equation is as follows
By increasing the substrate concentration, the rate of reaction will increase due to the likelihood that the number of enzyme-substrate complexes will increase; this occurs until the enzyme becomes the limiting factor.
