Properties of Enzymes

Enzyme-Substrate specificity 

Lock and Key Model 

Mechanism of Enzyme Action

Enzymes are highly specific in their function, meaning each enzyme catalyzes a particular reaction or a group of closely related reactions. This specificity arises from the unique three-dimensional structure of the enzyme, particularly the region known as the active site.

• The active site is a pocket or crevice on the enzyme’s surface where the substrate molecule(s) bind. 

This active site has a highly specific shape and chemical environment that is complementary to the shape and properties of the substrate molecule(s).

The active site is often compared to a lock, and the substrate is the key. Just as a key fits into a lock with precision, the substrate fits into the active site of the enzyme due to complementary shapes and chemical interactions.

• When the substrate molecules approach the enzyme, they bind to the active site through various types of chemical bonds such as hydrogen bonds, ionic bonds, and van der Waals forces. This binding is facilitated by the precise matching of the shapes and chemical properties of the active site and the substrate. The enzyme-substrate complex is formed, where the substrate is held in a position favorable for the reaction to occur.

• Once the substrate is bound to the active site, the enzyme catalyzes the conversion of the substrate(s) into product(s) by lowering the activation energy required for the reaction to proceed. This might involve breaking chemical bonds in the substrate(s) and forming new bonds to create the product(s). The enzyme provides an alternative reaction pathway that has a lower activation energy, allowing the reaction to occur more rapidly.

•  After the reaction, the products have different chemical properties compared to the substrate(s) and thus do not bind as strongly to the active site. As a result, they are released from the enzyme, leaving the active site available to bind new substrate molecules and repeat the catalytic cycle.

• The shape and chemical environment of the active site not only determine the specificity of the enzyme but also play a crucial role in regulating the enzyme’s activity. 

Factors such as pH, temperature, and the presence of inhibitors or activators can influence the shape and stability of the active site, thereby affecting enzyme activity.