Enzymes - Structure, Classification, Lock and Key Mechanism, Mechanism of Enzyme Reaction, Factors Affecting Enzyme Activity & Functions, Practice Problems and FAQs

Have you ever thought about what happens to the food that we eat? Where does it go? How does it break into smaller pieces? How is it digested?

Did you know that the digestion of the food starts from the mouth itself! Of course, chewing helps. But there is also a chemical breakdown of food that starts in the mouth. What is the chemical responsible for this? Well, it is a type of chemical which is present in your secretion, by the name of “enzymes''. Salivary amylase, in particular, aids in the breakdown of the carbohydrates found in diet. Look at the illustration provided below. Enzymes involved in the breakdown of carbohydrates, proteins, and lipids are displayed below.

Our bodies contain a variety of enzymes that catalyse various processes. But what exactly are the enzymes made of? What is its structure? What role does its structure play in catalysing any reaction?

Let’s understand everything about enzymes in detail!

Table of content:

• What areEnzymes?
• Structure of Enzymes
• Classification of Enzymes
• Lock and Key Mechanism
• Mechanism of Enzyme Reaction
• Factors Affecting Enzyme Activity
• Functions of Enzymes
• Practice Problems
• Frequently Asked Questions - FAQs

What are Enzymes?

"Biological polymers that catalyse the biochemical reactions are known as enzymes."

The majority of enzymes are catalytic proteins, which are needed to complete a variety of processes. The metabolic activities and other chemical reactions in the cell are carried out by a collection of enzymes, which are essential for life. The arrangement of amino acids is extremely precise and one-of-a-kind, involving hundreds of thousands of amino acids.

Enzymes can be present in all of the body's cells. Enzymes catalyse all the metabolic reactions taking place in the body. Enzymes are responsible for the majority of life's critical processes.

Structure of Enzymes:

The majority of enzymes are proteins, excluding ribozymes (composed of RNA). They are distinct and have a three-dimensional tertiary structure. The tertiary structure of peptide chains takes the shape of fissures or pockets after repeated folding or supercoiling. The term "active site" refers to the nooks or crannies where the substrate fits. The area of the active site where the substrate is bound is known as the substrate-binding site. A specific substrate can bind to a particular active site of an enzyme through weak interactions because the active site is substrate-specific. The structure and operation of proteins are determined by their amino acid composition. As a result, a change in amino acid sequence alters the structure of the enzyme and its active site. As a result, its function is altered.

Classification of enzymes:

Enzymes are categorised by the sort of reaction they are employed to catalyse into six functional classes, according to the International Union of Biochemists (I U B). Hydrolases, oxidoreductases, lyases, transferases, ligases, and isomerases are the six different categories of enzymes.

The classification of enzymes is covered in detail below:

Lock and Key mechanism:

The lock and key mechanism is a metaphor for the distinct nature of an enzyme's active site and substrate. Only specific substrates are compatible with the enzyme's active site, just as certain keys work with certain locks. An Enzyme substrate is formed when an appropriate substrate is attached to the enzyme's active site. The enzyme catalyses the process, resulting in the formation of an Enzyme Products Complex and the subsequent release of the products. The enzyme can be used multiple times to catalyse various reactions.

w reaction:

The primary mechanism of enzyme function is to catalyse chemical reactions, which start with the substrate attaching to the enzyme's active site. This active site is a specific location where the substrate interacts.

When the substrate () binds to the active site, a complex (intermediate-) is formed, which creates the product () and the enzyme (). The substrate that the enzyme attaches to has a specific structure that can only fit in a specific enzyme. As a result, by providing a surface for the substrate, an enzyme reduces the reaction's activation energy. The transition state is the intermediate stage in which the substrate interacts with the enzyme. The substrate joins the enzyme (which remains intact) as the bonds are broken and made, converting into the product, which then divides into product and enzyme. The liberated enzymes then bind to other substrates, continuing the catalytic cycle until the reaction is finished.

The enzyme action is divided into two stages:

Step 1:The enzyme and the reactant/substrate are combined.

Step 2:The complicated molecule is disintegrated to produce the finished product.

As a result, the entire enzyme catalyst action can be summarised as:

Factors affecting enzyme activity:

Following factors can affect enzyme activity:

• Active site
• Temperature and pH

Let’s now try to understand them in detail.

1. Active site:

The activity of amino acid side chains organised in the active core is required for enzyme catalysis. Enzymes bind the substrate to a portion of the active site. The active site is frequently a cleft or a pocket formed by amino acids involved in catalysis and substrate binding.

2. Temperature and pH:

Enzymes function best at a specific temperature and pH. The temperature or pH at which a substance exhibits maximum activity is known as the optimal temperature or pH. Enzymes are protein molecules, as previously stated. The molecular structure of enzymes will be altered if temperature or pH will be higher than ideal. The ideal pH for enzymes is generally thought to be between 5 and 7.

Functions of enzymes:

In the human body, enzymes serve a variety of purposes. Among them are:

1. Signal transduction is facilitated by enzymes. Protein kinase, which catalyses the phosphorylation of proteins, is the most prevalent enzyme utilised in the process.
2. They break down huge chemicals into tiny molecules that the body can easily absorb.
3. They aid in the body's energy production. The enzymes involved in energy synthesis are known as ATP synthase.
4. It controls the movement of ions across the plasma membrane.
5. To eliminate non-nutritive substances from the body, enzymes undertake a variety of biochemical reactions such as oxidation, reduction, hydrolysis, and others.
6. They govern cellular processes by reorganising the internal structure of the cell.

Practice problems:

Q1: What are exo- and endoenzymes?

Answer: Exo-enzymes are enzymes that work outside of living cells, such as those found in digestive fluids and tears' lysozyme. Endoenzymes are enzymes that work inside living cells, such as those found in the Krebs cycle (inside mitochondria) and glycolysis (inside cytoplasm).

Q2: Which of the following is incorrect for enzymes?

1. Enzymes are highly specific.
2. Enzymes require optimum pH for maximal activity
3. Most of the enzymes are proteins but some are lipids
4. Enzymes are denatured at high temperatures but in certain exceptional organisms they are effective even at temperatures from 80°–90°C

Answer: (B)

Solution: Most enzymes like a pH of 7. The pH at which an enzyme is most active is called the optimal pH. There is no universal guideline; it all depends on the specific enzyme in question. Human pepsin, for example, catalyses the process at a high acidic pH (1.5 to 3), whereas trypsin's optimal pH ranges from 7 to 9. (neutral to basic).

So, Option B is the correct answer.

Q3: Zn is an activator of the enzyme

1. Carboxypeptidase
2. Carbonic anhydrase
3. Carboxylases
4. All of these

Answer: (D)

Solution: Zinc is required for immunological function and activates protein metabolism enzymes. It is also a component of carbonate dehydratase and carbon dioxide transfer. It acts as an activator for carboxypeptidase, carbonic anhydrase and carboxylase.

So, Option D is the correct answer

Q4: During an enzymatic process, the transition state structure of the substrate is

1. Transient and unstable
2. Permanent but unstable
3. Permanent and stable
4. Transient but stable

Answer: (A)

Solution: The transition state is an unstable intermediate state created during an enzyme biological reaction.

So, Option A is the correct answer

Q5: What are digestive enzymes? Name them.

Answer: Digestive enzymes are a set of enzymes that break down polymeric macromolecules (food molecules) into smaller components (building blocks) to help the body absorb them. Hydrolases are the most common digestive enzymes found in the digestive systems of all animals (including humans) and carnivorous plants. Some of the important digestive enzymes are:

1. Amylase
2. Protease
3. Lipase
4. Nuclease

Frequently asked questions-FAQs:

Q1: What are the diseases caused by the deficiency of enzymes in the body?

Answer: The majority of enzymes are catalytic proteins, which are needed to complete a variety of processes. The metabolic activities and other chemical reactions in the cell are carried out by a collection of enzymes, which are essential for life. Albinism and phenylketonuria are the two diseases caused due to deficiency of enzymes.

Q2: What is the significance of an enzyme's structure?

Answer: The structure and shape of an enzyme are significant because they define which types of metabolic processes are possible based on the specificity of the substrate-bound to the enzyme's active site.

Q3: What is an enzyme's structure and function?

Answer:Enzymes are biocatalysts, which are organic catalysts that catalyse biochemical reactions at a specified biological temperature. They control the rate of biological reactions without participating in them. Its purpose is to accelerate metabolic reactions.

Q4: What is the function of the enzyme complex zymase?

Answer:The yeast enzyme complex zymase is utilised in the brewing or fermentation of alcoholic beverages.