Enzymes are the chemical substances essential for all life processes. They are the macromolecules that fasten up a biochemical reaction in a body. All enzymes are highly-specific so, they can speed up both the peculiarity and rate of metabolic reactions. In this article, we will discuss an enzyme, regulatory enzyme, and its major types.
The selective chemical compounds found in all plants and animals with heavy molecular mass are called enzymes. The principal role of an enzyme is to enhance or speed up a chemical reaction without changing its activity. They are mostly released from the ductal glands. All enzymes are proteins in nature except for Ribozyme. Besides, people are utilizing enzymes synthetically in fermentation, preservatives, baking, textiles, and other industries, etc.
What are Regulatory Enzymes?
As the name indicates, regulatory enzymes controls/regulates the activity of a biochemical pathway. These enzymes manage the byways of those reactions whose products are usually needed at regular intervals in various amounts.
For instance: Different hormones are produced and regulated through sequential metabolic pathways. Such activities are handled by a group of regulatory enzymes.
Why Is There a Need for Enzyme Regulation?
Every individual cell has its cellular needs and limitations, which vary with time. For example, the enzymatic requirement of a liver cell differs from those of stomach cells, blood cells, fat storage cells, and nerve cells. Similarly, a digestive mechanism would require more enzymes for the breakdown of a meal just after a person ate it than many hours after a meal. Just as these cellular mechanisms and demands vary, their functioning also varies. Hence, regulatory enzymes play a significant role in all life processes.
Types of Enzyme Regulation
Enzymes respond to different signals and are specific towards them. They can be classified into two major types based on the signals they respond to. Regulatory enzymes can be
- Allosteric Regulation
- Covalent Enzyme Regulation/Modification
This type of enzyme regulation works by binding to an enzyme other than the active site. Allosteric enzymes are formed from one or more than one protein subunit. The place where allosteric regulation occurs is called the allosteric site. Furthermore, the enzymes utilized in allosteric regulation can be activators or inhibitors.
As the name suggests, these enzymes bind to the allosteric site to enhance the cellular activity in a body. Sometimes, a substrate can personally work as an activator in the process known as cooperativity.
Unlike the above activators, these inhibitors attach to an enzyme on an allosteric site to decrease its activity. Such inhibitors can further be classified as competitive or non-competitive.
Due to these activators or inhibitors, allosteric regulation typically shows two main effects as below:
- Positive Feedback Effect
- Negative Feedback Effect (Feedback Inhibition)
As the allosteric activator boosts up an enzymatic activity, it shows a positive feedback effect. On the other hand, inhibitors reduce the enzyme regulation activity, leading towards feedback inhibition.
Covalent Enzyme Regulation
This type of enzyme regulation is held by the entry of other covalent molecules. When some other proteins or molecules attaches to enzymatic activity, they modify the reaction and regulates it. There are two types of the covalent modification seen as:
Reversible Covalent Enzyme Regulation:
When a covalent molecule interferes in a metabolic pathway, it plays a significant role. Reversible modification indicates that the enzymatic activity can bounce back to what it used to be. Such type of enzyme regulation demands extra energy to send and receive extracellular messages. Numerous mechanisms can bring modifications in enzymatic activity.
- Phosphorylation of certain threonine, serine, or tyrosine groups
- Methylation (addition of methyl group) of aspartate or glutamate residues
- Acetylation (addition of acetyl group) & Nucleotidylation of amino-terminal or lysine groups
Let us briefly discuss one example, i.e., Phosphorylation & Dephosphorylation.
Phosphorylation & Dephosphorylation
In general, Phosphorylation is the regulatory mechanism in a body by adding phosphate groups to proteins. Such processes hold significant importance in both eukaryotic and prokaryotic cells to regulate the living body processes.
The addition and elimination of a phosphoryl group to an enzyme are catalyzed by some enzymes, which are kinase and phosphatase enzymes. Moreover, these enzymes are functional all the time to regulate metabolic activity through either phosphorylation or dephosphorylation.
Irreversible Covalent Enzyme Regulation
When an enzyme cleaves an activity to perform its action, the process turns irreversible. Covalent enzyme regulation can be irreversible, such as, in proteolytic cleavage, the peptide bonds are utilized to modify an enzymatic activity.
Even after reading about the main types of enzyme regulation, just remember there can be numerous mechanisms still involved. They can be either activate or deactivate the enzyme regulation. The allosteric and covalent enzyme regulation attains large importance in speeding up or limiting a chemical reaction. They are not only used separately in a body but can also work in combination for modification.