∞ generated and posted on 2016.12.04 ∞
Location within a protein, typically an enzyme, that binds specifically to a substrate and where catalysis is effected.
Usually the active site will constitute only a very small portion of a protein. The rest of the protein is responsible for (1) stabilizing the active site, (2) interacting with other molecules (thereby helping to define where the protein is located in a cell), (3) effecting movement within the active site (thereby allowing the active site to change in conformation in response to substrate presence), and (4) controlling the activity of the active site, that is, whether or not catalysis can occur.
Figure legend: Diagrammatic representation of an enzyme with the active site shown as a small cleft. Note that substrate enters the active site but leaves as product. Within the active site the substrate is that being manipulated chemically, particularly in a manner that causes the substrate first to resemble and then to chemically become the product.
It is kind of like your computer. Only a very small portion of the computer is the actual processing unit. Everything else exists as various forms of support for that processing unit—so too most of an enzyme serves in a supporting roles for the active site, i.e., where the "action" really occurs.