Enzyme Function and Catalytic Properties

Properties of Enzymes as Biological Catalysts

An enzyme is a biocatalyst biologically synthesized by the body whose chemical composition is wholly or partially composed of protein. These biocatalysts are substances that are not consumed in the chemical reactions they facilitate; they work by lowering the activation energy, thus increasing the speed of the reaction.

The Mechanism of Enzyme Action

In general, the mechanism of enzyme action always takes place with the substrate binding, forming an intermediate enzyme complex (or enzyme-substrate complex) between them, without which the chemical reaction cannot take place. The enzymatic reaction can be symbolized as follows:

The substrate is any substance or molecule that acts as a reagent in the enzymatic reaction and specifically binds to the enzyme. The product is the molecule that occurs as a result of the reaction catalyzed by the enzyme. The catalytic mechanism of action of an enzyme is determined by its three-dimensional tertiary structure, which ensures the enzyme is specific to the substrate on which it acts. The enzyme-substrate binding occurs through weak intermolecular forces of nature that take place in a specific area of the enzyme called the active site.

The Role of the Active Site

The active site of the enzyme is directly responsible for the specific catalytic action, although the rest of the enzyme molecule is also important for maintaining the integrity of the whole structure.

Factors Affecting Enzyme Activity

Enzyme kinetics studies the variations of the catalytic reaction rate. This rate depends on a number of factors, including:

• Temperature
• pH levels
• Substrate concentration
• Activators
• Inhibitors

The pH is a factor that modulates the activity of enzymes, as these have two values between which they are effective. If these pH values are exceeded, the enzyme is denatured and thus loses its biological function. As for temperature, if heat energy is supplied to an enzymatic reaction, it is captured by the molecules involved and transformed into kinetic energy. This results in enhanced molecular mobility, increasing the number of collisions or contacts between molecules, which helps speed up the reaction. However, an excessive increase in temperature can lead to a distortion of the enzyme because of its protein nature.

Inhibitors and Activators

Enzyme inhibitors decrease or inhibit the enzymatic velocity, as they are able to reduce the activity and effectiveness of the enzyme. Finally, the action of activators is the reverse of inhibitors; they increase, therefore, the overall enzyme activity.