Enzymes, their nomenclature and functions in human bodies ~ Study Notes, Exams Guide, and Carrier Paths

Hi knowledge lovers! Here in this post you will find basic to advanced level information about one of the most important biological molecule "enzymes". The topics we are going to explore will cover most widely used terms and phenomenons in many exams, such as, BS Nursing, NMDCAT, entry tests preps, BS Biochemistry, NEETS, and other like these.

Enzymes are found in all cells and perform a vast array of biochemical tasks, such as digesting food, synthesizing hormones, and repairing tissues. In this blog post, we will explore the role of enzymes in living organisms and learn about the different types of enzymes and the reactions they catalyze. We will also delve into the classification, structure and function of enzymes, and how they are regulated and controlled.

enzymes-and-their-types-and-functions-of-enzymes-for-medical-students-nursing-paramedics-nutrition-bs-biochemistry

An all in one article on Enzymes for Healthcare Professionals and General Readers.
Presented by : H.E.S (Health, Education, and Skills)

A. Introduction to Enzymes

The study of enzymes and their function is known as enzymology, and is a key area of research in biochemistry.

Following are the main points to remember about enzymes

Enzymes are complex proteins that are made up of one or more polypeptide chains, which are long chains of amino acids (the building blocks of proteins) linked by peptide bonds. that catalyze chemical reactions in living organisms.
They are essential for the metabolic processes that sustain life, including the breakdown of molecules for energy production, the synthesis of new molecules, and the regulation of these processes.
Enzymes are highly specific and efficient catalysts, meaning they can speed up chemical reactions without being consumed or changed in the process. (This allows them to facilitate a wide range of chemical reactions within living organisms, including those that would be too slow or difficult to occur otherwise).
Enzymes are classified based on the type of reaction they catalyze, such as hydrolases, which break down molecules by adding water; transferases, which transfer chemical groups from one molecule to another; and ligases, which join molecules together.
Enzymes are also classified based on the type of substrate they act on, such as carbohydrates, lipids, or nucleic acids.
Defects in enzymes or the pathways they participate in can lead to various diseases and disorders.
Enzymes are sensitive to their environment and can be affected by factors such as temperature, pH, and the presence of inhibitors or activators.
The sequence of amino acids in the polypeptide chain determines the specific three-dimensional structure of the enzyme, which is crucial for its function.

B. How do enzymes catalyze the biochemical reactions?

Enzymes catalyze biochemical reactions by providing a specific environment that lowers the energy required for the reaction to occur known as energy of activation or activation energy. This allows the reaction to proceed more efficiently and at a faster rate.

Here's a more detailed explanation

1. The substrate(s) bind to the enzyme's active site:

The active site is a small pocket or groove on the surface of the enzyme that is complementary in shape and charge to the substrate(s). When the substrate(s) bind to the active site, the enzyme promotes the formation of a transition state.

2. The transition state is formed:

The transition state is an unstable intermediate stage in which the bonds in the substrate are partially broken and partially formed. It has a higher energy level than the reactants or products.

3. The enzyme stabilizes the transition state:

By stabilizing the transition state through specific interactions at the active site, the enzyme lowers the energy of activation.

4. The product(s) are formed and the enzyme is unchanged:

Once the reaction is complete, the product(s) are formed and the enzyme is unchanged, ready to catalyze another reaction with the same or a different substrate.

C. Structures of Enzyme

The specific three-dimensional structure of an enzyme is determined by the sequence of amino acids in its polypeptide chain(s) and the presence and arrangement of prosthetic groups. This structure is crucial for the enzyme's function, as it determines the shape and properties of the active site, where the substrate(s) bind and the reaction takes place.

D. Enzymes Classification | On the basis of type of reaction they catalyzes and the type of substrate it acts on.

Enzymes are classified and named using a standardized nomenclature system called the Enzyme Commission (EC) system. This system is based on the type of reaction that the enzyme catalyzes and the type of substrate it acts on.

Enzymes Commission System - EC System

The EC system is administered by the International Union of Biochemistry and Molecular Biology (IUBMB)
IUBMB is widely used in the field of biochemistry and molecular biology to identify and describe enzymes.
It is based on the work of the Enzyme Commission, a group of scientists who were appointed in 1955 to develop a system for naming enzymes.
The EC system is also widely used in scientific literature and databases, and is an important tool for organizing and communicating information about enzymes.
It helps to ensure that enzymes are consistently and accurately named and classified, making it easier to search for and compare information about specific enzymes.

According to EC nomenclature system enzymes are classified into the following six main categories, which are further divided into sub-classes and sub-sub classes, based on the type of reaction they catalyze:

1. Oxidoreductases

Enzymes that catalyze oxidation-reduction reactions are known as Oxido-reductase enzymes.

There are many subtypes of oxidoreductase enzymes, and they can be further classified based on the specific substrate that they act on and the type of redox reaction that they catalyze. These include

A. Dehydrogenases:

Dehydrogenases are a type of oxidoreductase enzyme that catalyze the removal of hydrogen atoms from a molecule.

They are involved in a wide range of important biochemical reactions, including the metabolism of carbohydrates, lipids, and amino acids. They are further into following categories

Alcohol dehydrogenases: These enzymes catalyze the oxidation of alcohols to aldehydes or ketones.
Aldehyde dehydrogenases: These enzymes catalyze the oxidation of aldehydes to carboxylic acids.
Lactate dehydrogenases: These enzymes catalyze the conversion of pyruvate to lactate.
Glutamate dehydrogenases: These enzymes catalyze the conversion of glutamate to alpha-ketoglutarate.
Succinate dehydrogenases: These enzymes are involved in the citric acid cycle and catalyze the conversion of succinate to fumarate.
Malate dehydrogenases: These enzymes catalyze the conversion of malate to oxaloacetate.

On the basis of presence or absence of Oxygen for a reaction, dehydrogenases are classified as

a. Aerobic dehydrogenases are enzymes that catalyze the removal of hydrogen atoms from a molecule using oxygen as an electron acceptor. These reactions occur in the presence of oxygen and produce water as a byproduct.

b. Anaerobic dehydrogenases are enzymes that catalyze the removal of hydrogen atoms from a molecule without using oxygen as an electron acceptor. These reactions occur in the absence of oxygen and produce other compounds as byproducts, such as alcohols or organic acids.

Both aerobic and anaerobic dehydrogenases play important roles in the metabolism of cells. They are involved in processes such as respiration, fermentation, and the breakdown of nutrients to produce energy.

B. Oxidases:

Oxidase enzymes are a type of oxidoreductase enzyme that increases the oxidation state of a molecule by removing electrons from it.They use only Oxygen as hydrogen acceptor.

They are involved in a wide range of important biochemical reactions, including the metabolism of carbohydrates, lipids, and amino acids.

There are several different types of oxidase enzymes, including:

Cytochrome oxidase: This enzyme is involved in the electron transport chain and catalyzes the transfer of electrons from cytochrome c to oxygen.
Diamine oxidase: This enzyme oxidizes diamines to aldehydes.
Laccase: This enzyme oxidizes a wide range of substrates, including phenols, anilines, and polyphenols.
Monoamine oxidase: This enzyme oxidizes monoamines to aldehydes.
Xanthine oxidase: This enzyme catalyzes the oxidation of hypoxanthine to xanthine and xanthine to uric acid.
Alcohol oxidase: This enzyme oxidizes primary and secondary alcohols to aldehydes and ketones, respectively.

C. Oxygenases:

Oxygenase enzymes are a type of oxidoreductase enzyme that add oxygen atoms to a molecule. They are also involved in a wide range of important biochemical reactions, including the metabolism of carbohydrates, lipids, and amino acids.

There are several different types of oxygenase enzymes, including:

Cytochrome P450 oxygenases: These enzymes are involved in the metabolism of a wide range of substances, including drugs, hormones, and toxins.
Dioxygenases: These enzymes catalyze the addition of two oxygen atoms to a substrate.
Monooxygenases: These enzymes catalyze the addition of one oxygen atom to a substrate.
Amino acid oxygenases: These enzymes catalyze the addition of an oxygen atom to an amino acid.
Lipoxygenases: These enzymes catalyze the addition of an oxygen atom to a fatty acid.
Phenylalanine hydroxylase: This enzyme catalyzes the addition of an oxygen atom to phenylalanine, which is an important step in the metabolism of this amino acid.

D. Hydrogen Peroxidases

Hydrogen peroxide is a molecule that consists of two hydrogen atoms bonded to two oxygen atoms. It is a powerful oxidizing agent and is used in a variety of industrial and medical applications.

Hydrogen peroxidases are a type of enzyme that catalyze the breakdown of hydrogen peroxide into water and oxygen.

There are several different types of hydrogen peroxidases, including:

Catalase: This enzyme is found in the cells of many organisms and catalyzes the breakdown of hydrogen peroxide into water and oxygen.
Glutathione peroxidase: This enzyme is found in the cells of many organisms and catalyzes the breakdown of hydrogen peroxide with the help of the antioxidant glutathione.
Myeloperoxidase: This enzyme is found in the cells of the immune system and catalyzes the breakdown of hydrogen peroxide as part of the process of killing invading microorganisms.
Peroxidases: These enzymes are found in a variety of tissues and catalyze the breakdown of hydrogen peroxide as well as other peroxides.
Thioredoxin peroxidase: This enzyme is found in the cells of many organisms and catalyzes the breakdown of hydrogen peroxide with the help of the protein thioredoxin.
Tyrosinase: This enzyme is found in the cells of many organisms and catalyzes the breakdown of hydrogen peroxide as well as the oxidation of tyrosine, an amino acid

2. Transferases:

Transferases are a type of enzyme that catalyze the transfer of a specific group of atoms (Except Hydrogne Molecule) from one molecule to another.

There are many different types of transferases, and they can be classified based on the type of group that they transfer and the specific reaction that they catalyze e.g Transaminases, Phosphotransaferases, Transmethylases, Transpeptidases, and Transacylases. Their detail is given below

A. Transaminases

Transaminases are a type of enzyme that catalyze the transfer of an amino group (NH2) from one molecule to another. The exchange of amino group take place between an amin acid and a keto acid as a result amino acid become keto acid and keto acid become amino acid. They are involved in a wide range of important biochemical reactions, including the metabolism of amino acids and the synthesis of proteins.

There are several different types of transaminases, including:

Alanine transaminase (ALT) or SGPT (Serum Glutamate Pyruvate Transaminase): This enzyme transfers an amino group from alanine to alpha-ketoglutarate, producing pyruvate and glutamate.
Aspartate transaminase (AST) or SGOT (Serum Glutamate Oxaloacetate Transaminase) : This enzyme transfers an amino group from aspartate to alpha-ketoglutarate, producing oxaloacetate and glutamate.
Glutamate transaminase (GPT): This enzyme transfers an amino group from glutamate to alpha-ketoglutarate, producing 2-oxoglutarate and aspartate.
Arginine transaminase: This enzyme transfers an amino group from arginine to alpha-ketoglutarate, producing ornithine and glutamate.
Lysine transaminase: This enzyme transfers an amino group from lysine to alpha-ketoglutarate, producing saccharopine and glutamate.
Histidine transaminase: This enzyme transfers an amino group from histidine to alpha-ketoglutarate, producing imidazoleacetate and glutamate

Significance of Transaminases

They help in the formation of non-essential amino acids e.g. alanine and aspartate.
Alanine is converted to pyruvate, which is a substrate for gluco-neo-genesis.

B. Phosphotransaferase

Phosphotransferases are a type of enzyme that catalyze the transfer of a phosphate group from one molecule to another.

There are several different types of phosphotransferases, including:

Kinases: These enzymes transfer a phosphate group from ATP to another molecule.
Phosphofructokinases: These enzymes transfer a phosphate group from ATP to fructose-6-phosphate, producing fructose-1,6-bisphosphate and ADP.
Hexokinases: These enzymes transfer a phosphate group from ATP to glucose, producing glucose-6-phosphate and ADP.
Phosphoglucomutases: These enzymes transfer a phosphate group from glucose-6-phosphate to glucose, or vice versa.
Phosphotransferases: These enzymes transfer a phosphate group from a molecule of 3'-phosphoadenosine-5'-phosphosulfate (PAPS) to another molecule.
Phosphoglucoisomerases: These enzymes catalyze the isomerization of glucose-6-phosphate to fructose-6-phosphate.

C. Transmethylases

Transmethylases are a type of enzyme that catalyze the transfer of a methyl group from one molecule to another. They are involved in a wide range of important biochemical reactions, including the metabolism of amino acids and the synthesis of compounds such as hormones and neurotransmitters.

There are several different types of transmethylases, including:

S-Adenosylmethionine (SAM)-dependent methyltransferases: These enzymes transfer a methyl group from SAM to another molecule.
Dimethylallyltranstransferase: This enzyme transfers a methyl group from dimethylallyl diphosphate (DMADP) to another molecule.
Histone lysine N-methyltransferases: These enzymes transfer a methyl group from SAM to a lysine residue on a histone protein.
Protein lysine N-methyltransferases: These enzymes transfer a methyl group from SAM to a lysine residue on a protein.
Protein arginine N-methyltransferases: These enzymes transfer a methyl group from SAM to an arginine residue on a protein.
DNA cytosine N-methyltransferases: These enzymes transfer a methyl group from SAM to a cytosine base in DNA

D. Transpeptidases

Transpeptidases are a type of enzyme that catalyze the transfer of a peptide bond from one molecule to another. They are involved in a wide range of important biochemical reactions, including the synthesis of proteins and the modification of other biomolecules.

There are several different types of transpeptidases, including:

Carboxypeptidases: These enzymes hydrolyze a peptide bond at the carboxyl end of a protein or peptide.
Aminopeptidases: These enzymes hydrolyze a peptide bond at the amino end of a protein or peptide.
Peptidyl transferases: These enzymes transfer a peptide bond from one molecule to another, such as during the synthesis of proteins.
Penicillin-binding proteins: These enzymes are involved in the synthesis of the cell wall in bacteria and hydrolyze a peptide bond during this process.
Endopeptidases: These enzymes hydrolyze a peptide bond within a protein or peptide.
Exopeptidases: These enzymes hydrolyze a peptide bond at the ends of a protein or peptide.

E. Transacylases

Transacylases are a type of enzyme that catalyze the transfer of an acyl group from one molecule to another. They are involved in a wide range of important biochemical reactions, including the metabolism of carbohydrates, lipids, and amino acids.

There are several different types of transacylases, including:

Acyltransferases: These enzymes transfer an acyl group from one molecule to another.
Acyl-CoA synthetases: These enzymes transfer an acyl group from a carboxylic acid to CoA, forming an acyl-CoA molecule.
Acetyltransferases: These enzymes transfer an acetyl group from acetyl-CoA to another molecule.
Acyl-CoA thioesterases: These enzymes hydrolyze an acyl-CoA molecule to form a free carboxylic acid and CoA.
Acyl-CoA dehydrogenases: These enzymes transfer an acyl group from an acyl-CoA molecule to NAD+ or NADP+, producing an aldehyde or ketone and NADH or NADPH.
Fatty acid synthases: These enzymes synthesize fatty acids by transferring an acyl group from one molecule to another.

3. Hydrolases:

Hydrolases are a type of enzyme that catalyze the hydrolysis (break down) of a chemical compound by the addition of water into the substrate. They are further classified as

A. Protein Hydrolyzing Enzymes (Proteinases or Proteases or Proteolytic Enzymes)

Proteases are a type of hydrolase enzyme that catalyze the hydrolysis of proteins into peptides and amino acids. They are involved in a wide range of important biochemical reactions, including the digestion of food proteins, the activation of enzymes, and the regulation of various biological processes.

It has following two sub-types

i. Exopeptidases

Exopeptidases are a type of enzyme that catalyze the hydrolysis of peptide bonds at the ends of a protein or peptide.

There are several different types of exopeptidases, including:

Aminopeptidases: These enzymes hydrolyze peptide bonds at the amino end of a protein or peptide.
Carboxypeptidases: These enzymes hydrolyze peptide bonds at the carboxyl end of a protein or peptide.
Dipeptidases: These enzymes hydrolyze dipeptides (short chains of two amino acids) into individual amino acids.
Prolyl endopeptidases: These enzymes hydrolyze peptide bonds within proteins, specifically at the side of proline residues.
Leucyl aminopeptidases: These enzymes hydrolyze peptide bonds at the amino end of proteins, specifically at the side of leucine residues.
Prolyl aminopeptidases: These enzymes hydrolyze peptide bonds at the amino end of proteins, specifically at the side of proline residues

ii. Endopeptidases

Endopeptidases are a type of enzyme that catalyze the hydrolysis of peptide bonds within a protein or peptide.

There are several different types of endopeptidases, including:

Proteases: These enzymes hydrolyze proteins into peptides and amino acids.
Prolyl endopeptidases: These enzymes hydrolyze peptide bonds within proteins, specifically at the side of proline residues.
Leucyl endopeptidases: These enzymes hydrolyze peptide bonds within proteins, specifically at the side of leucine residues.
Trypsin: This enzyme hydrolyzes proteins by cleaving them at the side of lysine and arginine residues.

B. Carbohydrate Hydrolyzing Enzymes (Carbohydrases)

Carbohydrases are a type of enzyme that catalyze the hydrolysis of carbohydrates into simpler sugars.

There are several different types of carbohydrases, including:

Amylases: These enzymes hydrolyze starch and glycogen into glucose.
Lactases: These enzymes hydrolyze lactose into glucose and galactose.
Sucrase: This enzyme hydrolyzes sucrose into glucose and fructose.
Maltases: These enzymes hydrolyze maltose into glucose.
Isomaltases: These enzymes hydrolyze isomaltose into glucose.
Glucoamylases: These enzymes hydrolyze glucosyl units from the non-reducing ends of oligosaccharides and polysaccharides.

C. Lipids Hydrolyzing Enzymes

Lipids are a diverse group of biomolecules that includes fats, oils, waxes, and other related compounds. There are several enzymes that can hydrolyze lipids, breaking them down into simpler molecules.

a. Lipases: Lipases are a type of enzyme that catalyze the hydrolysis of lipids, such as triglycerides, into fatty acids and glycerol.

There are several different types of lipases, including:

Pancreatic lipases: These enzymes are produced by the pancreas and are responsible for the digestion of fats in the small intestine.
Hormone-sensitive lipases: These enzymes are activated by hormones such as adrenaline and are involved in the breakdown of fats in adipose tissue.
Lipoprotein lipases: These enzymes hydrolyze lipids in lipoproteins, such as very low-density lipoproteins (VLDL) and chylomicrons.
Lecithin-cholesterol acyltransferases (LCAT): These enzymes transfer fatty acids from lecithin to cholesterol, forming cholesterol esters.
Lipase A: This enzyme hydrolyzes lipids in the outer membrane of bacteria.
Lipase B: This enzyme hydrolyzes lipids in the inner membrane of bacteria.

b. Cholesterases: Cholesterases are enzymes that catalyze the hydrolysis of cholesterol and related compounds.

There are several different types of cholesterases, including:

Cholesteryl ester hydrolases: These enzymes hydrolyze cholesteryl esters, such as cholesterol esters, into free cholesterol and a fatty acid.
HMG-CoA reductases: These enzymes catalyze the reduction of 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) to mevalonate, a key step in the synthesis of cholesterol.
LDL receptors: These receptors bind to low-density lipoproteins (LDL) and internalize cholesterol, leading to its degradation.
ACAT (acyl-CoA:cholesterol acyltransferase): These enzymes transfer an acyl group from an acyl-CoA molecule to cholesterol, forming a cholesteryl ester.
CETP (cholesteryl ester transfer protein): This protein transfers cholesteryl esters from high-density lipoproteins (HDL) to other lipoproteins, such as VLDL and LDL.
SR-BI (scavenger receptor class B type I): This receptor binds to HDL and mediates the uptake of cholesterol by cells

c. Phospholipases (Previously called Lecithinases): Phospholipases are a type of enzyme that catalyze the hydrolysis of phospholipids, such as lecithin, into fatty acids, glycerol, and a phosphate group.

There are several different types of phospholipases, including:

Phospholipase A1: This enzyme hydrolyzes the sn-1 position of phospholipids, producing a fatty acid and lysophospholipid.
Phospholipase A2: This enzyme hydrolyzes the sn-2 position of phospholipids, producing a fatty acid and lysophospholipid.
Phospholipase B: This enzyme hydrolyzes the sn-1,2 positions of phospholipids, producing diacylglycerol and a phosphate group.
Phospholipase C: This enzyme hydrolyzes the sn-3 position of phospholipids, producing diacylglycerol and a phosphate group.
Phospholipase D: This enzyme hydrolyzes the sn-1 position of phospholipids, producing phosphatidic acid and a fatty alcohol.
Phospholipase E: This enzyme hydrolyzes the sn-2 position of phospholipids, producing a lysophospholipid and a fatty alcohol.

D. Deaminases or Aminohydrolases

Deaminases are a type of enzyme that catalyze the removal of an amino group from a molecule.

There are several different types of deaminases, including:

Adenine deaminases: These enzymes remove the amino group from adenine, producing hypoxanthine.
Cytosine deaminases: These enzymes remove the amino group from cytosine, producing uracil.
Histidine deaminases: These enzymes remove the amino group from histidine, producing urocanic acid.
Xanthine deaminases: These enzymes remove the amino group from xanthine, producing hypoxanthine.
Tyrosine deaminases: These enzymes remove the amino group from tyrosine, producing p-cresol.
Glutamine deaminases: These enzymes remove the amino group from glutamine, producing glutamate.

E. Deamidases or Amidohydrolases

Deamidases are enzymes that catalyze the removal of an amide group from a molecule. They are involved in a wide range of important biochemical reactions, including the metabolism of proteins and the synthesis of compounds such as nucleotides and purines.

There are several different types of deamidases, including:

Glutaminyl cyclase: This enzyme removes an amide group from the side chain of glutamine, producing an imine group and ammonia.
Peptide deformylase: This enzyme removes an amide group from the N-terminal of a peptide, producing a formyl group and the amino acid N-formylmethionine.
Carboxypeptidase E: This enzyme removes an amide group from the C-terminal of a peptide, producing a carboxyl group and the amino acid C-terminal valine.
Glutamate carboxypeptidase: This enzyme removes an amide group from the C-terminal of a peptide, producing a carboxyl group and the amino acid C-terminal glutamate.
Dipeptidyl peptidase IV: This enzyme removes an amide group from the side chain of dipeptides, producing two individual amino acids.
Asparagine deamidase: This enzyme removes an amide group from asparagine, producing aspartate.

F. Other Hydrolyzing Enzymes

There are two groups under this category

i. Phosphatases:

Phosphatases are enzymes that catalyze the hydrolysis of phosphate esters, such as ATP, into a free phosphate group and the molecule to which it was attached.

They are of the following types

Phosphomonoesterases: Split one phosphate group of a monoester. E.g Acid Phosphatases and alkaline phosphatases i.e. (a). Acid phosphatases: These enzymes hydrolyze phosphate esters at acid pH. (b). Alkaline phosphatases: These enzymes hydrolyze phosphate esters at alkaline pH.
Phosphodiesterases: Split off one phosphate group from diesters.
Phosphorylase: Add the phosphate group into the subsrate e.g. Glycogen Phosphorylase.
Pyrophosphatases: Remove pyrophosphate (two phosphatase) from the substrate e.g. ATPase.
Nucleases or Polynucleotidase : Decompose nucleic acids (DNA and RNA).
Nucleotidase : Hydrolyze mononucleotides to nucleosides.

ii. Miscellaneous

They are of the following types

Cholinesterases: Hydrolyze acetylcholine and other related substrate.
Sulfatases: Hydrolyze sulfate esters.

4. Ligases

Ligases are enzymes that catalyze the formation of a covalent bond between two molecules by transferring a group from one molecule to the other. They are involved in biochemical reactions, including the synthesis of nucleic acids and proteins, the repair of DNA, and the metabolism of carbohydrates and lipids.

There are several different types of ligases, including:

Nucleotidyl transferases: These enzymes transfer nucleotides to a nucleic acid template, synthesizing DNA or RNA.
Adenylate cyclases: These enzymes transfer a phosphate group from ATP to an acceptor molecule, forming cyclic AMP (cAMP).
Phosphotransferases: These enzymes transfer a phosphate group from a nucleoside triphosphate to an acceptor molecule.
Transferases: These enzymes transfer a group, such as an amino group or a sugar residue, from one molecule to another.
Synthetases: These enzymes synthesize a molecule, such as a protein or a nucleic acid, by joining smaller units together.

5. Lyases

Lyases are enzymes that catalyze the cleavage of a chemical bond by a mechanism other than hydrolysis or oxidation-reduction.

There are several different types of lyases, including:

Aldolases: These enzymes cleave aldoses or ketoses into two molecules by removing a carbon atom from the middle of the molecule.
Decarboxylases: These enzymes remove a carboxyl group from a molecule, producing a compound with one less carbon atom.
Desulfurases: These enzymes remove sulfur from a molecule, producing a compound with one less sulfur atom.
Deaminases: These enzymes remove an amino group from a molecule, producing a compound with one less nitrogen atom.
Dehydratases: These enzymes remove water from a molecule, producing a compound with one fewer oxygen and hydrogen atoms.

6. Isomerases

Isomerases are enzymes that catalyze the conversion of one isomer into another. Isomers are molecules that have the same molecular formula, but different structural arrangements of their atoms.

There are several different types of isomerases, including:

Epimerases: These enzymes convert one epimer into another. Epimers are isomers that differ in the configuration of one or more asymmetric carbon atoms.
Esterases: These enzymes catalyze the conversion of an ester into another isomer. Esters are compounds that are formed from the reaction of a carboxylic acid and an alcohol.
Racemases: These enzymes catalyze the conversion of a racemic mixture into a pure enantiomer. A racemic mixture is a mixture of equal amounts of two enantiomers, which are isomers that are mirror images of each other.
Dehydratases: These enzymes remove water from a molecule, producing a compound with one fewer oxygen and hydrogen atoms.
Epoxidases: These enzymes catalyze the conversion of an epoxide into another isomer. An epoxide is a cyclic compound with three atoms in a ring, one of which is oxygen.

Enzymes Classification | On the basis of their structures

Enzymes can be classified into two main types based on their structure:

A: Simple enzymes:

Simple enzymes are made up of a single polypeptide chain and do not have any prosthetic groups (non-protein components that are essential for enzyme function).

Here are a few examples of simple enzymes:

Lysozyme: Lysozyme is an enzyme that breaks down the cell walls of bacteria. It is found in the tears, saliva, and mucus of humans and other animals, and helps to protect against infections.
Chymotrypsin: Chymotrypsin is an enzyme that breaks down proteins into smaller peptides. It is found in the pancreas and small intestine, and is activated by the presence of trypsinogen.
Pepsin: Pepsin is an enzyme that breaks down proteins into smaller peptides. It is found in the stomach and is activated by the presence of hydrochloric acid.
Carbonic anhydrase: Carbonic anhydrase is an enzyme that catalyzes the reversible reaction between carbon dioxide and water to form bicarbonate and protons. It is found in various tissues and organs, including the pancreas and red blood cells.

B. Complex enzymes:

Complex enzymes are made up of two or more polypeptide chains, and may also have one or more prosthetic groups. The polypeptide chains may be held together by covalent bonds or non-covalent interactions.

Here are a few examples of complex enzymes:

Cytochrome c oxidase: Cytochrome c oxidase is an enzyme that catalyzes the reduction of oxygen to water during cellular respiration. It is made up of 13 subunits, including heme and copper prosthetic groups, and is found in the mitochondria of cells.
Fumarase: Fumarase is an enzyme that catalyzes the reversible reaction between fumarate and water to form malate. It is made up of four subunits and is found in the mitochondria and cytoplasm of cells.
Ribonucleotide reductase: Ribonucleotide reductase is an enzyme that synthesizes deoxyribonucleotides, which are needed for DNA synthesis. It is made up of two subunits and is found in the nuclei of cells.
Pyruvate dehydrogenase: Pyruvate dehydrogenase is an enzyme that converts pyruvate to acetyl-CoA, a key step in the production of energy in cells. It is made up of three subunits and is found in the mitochondria of cells.

Role of Enzymes in Human Body

Some examples of the roles that enzymes play in the human body include:

1. In Digestion

The digestion of food begins in the mouth, where saliva containing the enzyme amylase begins to break down carbohydrates. As the food moves through the digestive system, it is acted upon by various enzymes that help to break it down into smaller, more easily absorbed molecules.

There are several types of enzymes that are involved in the digestion of different types of nutrients:

Proteases: These enzymes break down proteins into smaller peptides and amino acids. Examples include trypsin, chymotrypsin, and pepsin.
Lipases: These enzymes break down lipids (fats) into fatty acids and glycerol. Examples include pancreatic lipase and gastric lipase.
Amylases: These enzymes break down carbohydrates (such as starch) into simpler sugars like glucose. Examples include pancreatic amylase and salivary amylase.
Lactases: These enzymes break down lactose (a sugar found in milk) into glucose and galactose.

2. Energy production:

Enzymes such as ATP synthase and pyruvate dehydrogenase play a key role in the production of ATP, the primary source of energy for the body.

One of the main ways that enzymes help to produce energy is through the process of cellular respiration, which occurs in the mitochondria of cells. During cellular respiration, glucose and other nutrients are broken down into energy-rich molecules of ATP (adenosine triphosphate) through a series of chemical reactions.

Some of the enzymes involved in energy production include:

Pyruvate dehydrogenase: This enzyme converts pyruvate (a product of glucose metabolism) into acetyl-CoA, which is then used in the production of ATP.
Alpha-ketoglutarate dehydrogenase: This enzyme converts alpha-ketoglutarate (a product of amino acid metabolism) into succinyl-CoA, which is then used in the production of ATP.
Fumarase: This enzyme converts fumarate into malate, which is then used in the production of ATP.
ATP synthase: This enzyme converts ADP (adenosine diphosphate) into ATP by adding a phosphate group

3. Detoxification

Some of the enzymes involved in detoxification include:

Cytochrome P450: This enzyme family is involved in the metabolism of drugs and toxins, including alcohol, caffeine, and certain pesticides.
Alcohol dehydrogenase: This enzyme breaks down alcohol into acetaldehyde, which is then further broken down into acetate.
Glutathione S-transferases: These enzymes help to detoxify harmful substances by conjugating them to glutathione, a small molecule that can be excreted in the urine.
Lactate dehydrogenase: This enzyme helps to break down lactate, a product of the metabolism of certain toxins, into pyruvate.

4. Hormone regulation

Hormones are chemical signaling molecules that are produced by glands and released into the bloodstream, where they act on specific target cells or tissues. Enzymes help to control the levels and activity of hormones by synthesizing them, breaking them down, or modifying them in some way.

Some of the enzymes involved in hormone regulation include:

Kinases: These enzymes add a phosphate group to a hormone or other protein, activating or inactivating it.
Phosphatases: These enzymes remove a phosphate group from a hormone or other protein, activating or inactivating it.
Aromatases: These enzymes convert androgens (male hormones) into estrogens (female hormones).
5'-Deiodinases: These enzymes convert thyroid hormones into their active form.
Peptidases: These enzymes break down peptide hormones into smaller peptides or amino acids.

5. Blood clotting

Enzymes such as thrombin and fibrinogen help to form blood clots to stop bleeding. Blood clotting is a complex process that involves the activation and interaction of several proteins and enzymes.

Some of the enzymes involved in blood clotting include:

Thrombin: This enzyme converts fibrinogen (a protein in the blood) into fibrin, a long, fibrous protein that helps to form a blood clot.
Factor XIII: This enzyme helps to crosslink the fibrin fibers, strengthening the blood clot.
Plasmin: This enzyme breaks down fibrin and other blood clotting factors, dissolving the blood clot once it is no longer needed.

6. DNA Replication

Enzymes play a crucial role in the process of DNA replication, which is the process by which cells create copies of their genetic material. DNA replication is necessary for the reproduction of cells and the maintenance of genetic information.

Some of the enzymes involved in DNA replication include:

DNA polymerase: This enzyme synthesizes a new DNA strand by adding nucleotides to the template strand.
Primase: This enzyme synthesizes a short RNA primer, which provides a starting point for DNA polymerase to begin synthesizing the new DNA strand.
Helicase: This enzyme unwinds the DNA double helix, separating the two strands.
Topoisomerase: This enzyme helps to relieve the strain that is generated during DNA replication by making cuts in the DNA strands and rejoining them.
Ligase: This enzyme seals gaps in the newly synthesized DNA strands.

Enzymes are essential for the proper replication of DNA, and a deficiency or dysfunction of certain enzymes can lead to problems with DNA replication and the maintenance of genetic information.