Enzyme Activators

Enzymes are biological molecules that act as catalysts that speed up the processes. They are protein sources that are formed by chains of amino acids in various combinations. Enzymes are highly specific in reactivity. There are thousands of enzymes in the human body that will catalyse various metabolic reactions occurring in the body. 

What are Enzymes?

Enzymes are usually globular proteins that are three-dimensional and produced by ribosomes and RNA (Ribo Nucleic Acids) of the cell. All enzymes have specific active sites on their surface, which works for a particular substrate. The substrate is the reacting species of a reaction that changes to form products. Every substrate and product has a certain energy. Some can have low energy, and some can have high energy. For the substrate to turn into products, the reacting particles need to cross the energy barrier called activation energy. This activation energy for all the substrate molecules may not be equal and results in fewer products and relatively takes a longer time to complete. 

To increase the rate of conversion of substrate to products, a small number of enzymes are used that are suitable for a reaction. This enhances the speed of the reaction by reducing the activation energy for the reaction.

Example 1: Saliva in the mouth produces saliva enzymes to enhance the digestion of food in the mouth.

Example 2: Formation of Ammonia

N2 + 3H2 → 2NH3

This reaction takes a relatively long time to complete; to speed up the process, an Iron (Fe) metal catalyst is used. In the same reaction, Molybdenum is used as a promoter.

Active Sites of Enzymes

Enzymes have active sites of specific shape as they have tertiary structures. A small change in the size or shape of the active site can change the activity of enzymes. Active sites of enzymes can be further classified as the binding site and catalytic site.

Binding site: This site chooses the substrate and binds it to the active site.

Catalytic site: This site performs the catalytic function of an enzyme.

Cofactors are the non-protein molecules that perform or catalyse reactions that are not carried out by 20 amino acids present in our body. Cofactors can be organic and inorganic.

Cofactors bind to the protein and make it active, whereas proteins without a cofactor protein are inactive.

Enzymes can be intracellular and extracellular. Intracellular are those that are produced in the body and retained for the functioning of the cell. Extracellular enzymes are those that are produced in the cell and sent outside of the cell to work externally.

Mechanism of Enzyme Action

Enzyme catalytic activity can be explained in terms of thermodynamic changes and processes at the active site.

Thermodynamic changes:

Every chemical reaction in the body or outside the body has a specific energy barrier between the reactant molecules and the product molecules. The energy difference between the reactants and products is said to be an activation barrier.

All the substrate molecules do not possess sufficient energy to cross the barrier, so most of the reactions without the catalyst are slow. Enzymes help in changing the path for the reactants to convert to products by reducing the activation barrier for the reactants and helping in crossing this barrier for many reactants and increasing the rate of reaction, and speeding up the process. The rate of the reaction with the catalyst increases to a large extent. The overall energy, which is the sum of energy of reactants and products, remains the same.

Processes at the active site:

Enzymes bind at the active site by covalent linkages with the substrate molecules and form an enzyme-substrate complex with very low activation energy and form products easily in a short time.

After the reaction, enzymes release and come to their original form without any changes.

Enzyme Activation

The conversion of an inactive enzyme to its active form by which the metabolic activities can be carried out is said to be enzyme activation. Activation of an enzyme can be done by cofactors and conversion of an enzyme precursor.

Activation by cofactors:

Most of the enzymes get activated by cofactors.

Example 1: DNA-Polymerase, which is a holoenzyme that uses Magnesium ion as a cofactor.

Example 2: Horse liver dehydrogenase uses Zinc ion as a cofactor.

Enzymes act in a highly specific manner. They have different degrees of specificity in terms of:

• Bonding specificity
• Group specificity
• Absolute specificity
• Optical or stereospecificity
• Dual specificity

Conversion of an enzyme precursor:

A common method of activating an enzyme is specific proteolysis, which is the breakdown of proteins into simpler amino acids.

Example: Proteolysis of trypsinogen forms trypsin which activates other zymogens.

Promoters

Promoters are the chemical components that help in increasing the activity of the enzymes. They help in the increased efficiency of enzymes. Promoters are usually taken in a small quantity along with the catalyst in a chemical reaction.

Example: In Haber’s process, this is the formation of Ammonia that uses Molybdenum as a promoter for the catalyst Iron.

Conclusion

Enzymes are the biomolecules that drive various reactions in and out of the body. These enzymes are activated by substances which are called enzyme activators. Without them, enzymes remain inactive.