Classification of enzyme - class-XI

ATP or adenosine triphosphate is a nucleotide. It is not a co-enzyme.

Transferases are the enzymes that catalyze group transfer reactions. In the figure, one group G has been transferred to another group S'. It is a classical example of a group transfer reaction.

The induced-fit model is proposed by Daniel Koshland in 1958. It is the most accepted model for enzyme-substrate complex. It describes the formation of the Enzyme substrate as a result of the interaction between the substrate and a flexible active site which means exposure of an enzyme to a substrate causes the active site of the enzyme to change shape in order to allow the enzyme and substrate to bind. Hence option C is correct.

Coenzymes are organic cofactors which are required for enzymatic action of certain enzymes. NADP is a coenzyme form of vitamin nicotinamide or niacin.

DNA polymerase is an enzyme used in DNA replication. It synthesizes DNA on a DNA template. Bacteria have three different DNA polymerases, i.e., DNA pol I, DNA pol II and DNA pol III; while eukaryotes have several DNA polymerase enzymes.

RNA polymerase participates in RNA synthesis during transcription process. It synthesizes RNA on DNA template.

According to the modern classification system given by International Union of Biochemistry, enzymes have been classified into six classes as follows :
Class First is Oxidoreductase.
Class Second is Transferase.
Class Third is Hydrolase.
Class Fourth is Lyase.
Class Fifth is Isomerase.
Class Sixth is Ligase.

Esterases are the enzyme which hydrolyse ester linkage. Hence, esterases belong to class Hydrolase. Hydrolases are the enzymes catalysing hydrolysis.

Dehydrogenases catalyze dehydrogenation reactions, which involve addition or removal of electrons. Addition or removal of electrons will lead to reduction or oxidation of substrates. Dehydrogenases are a type of oxidoreductases.

This question relates to the industrial applications of enzymes. Alcohol is not produced by the use of nitrogenase. Nitrogenase performs complex functions of nitrogen fixation by bacteria. Alcohol is produced by the fermentation process of sugars carried out by Yeast.

Dehydrogenases catalyze dehydrogenation reactions which involve addition or removal of electrons. The addition or removal of electrons will lead to reduction or oxidation of substrates. Dehydrogenases are a type of oxidoreductases. Some of the important hydrolases includes amylases, sucrase, lactase, maltase, protease, esterase etc.

Biochemical reactions are unique because they are mediated by enzymes, which lower activation energy and increase reaction rates under physiological conditions.

Some enzymes have several molecular forms, example: 16 for $\alpha$-amylase and 5 for lactate dehydrogenase (LDH). They are called as isoenzymes or isozymes. They differ in substrate affinity, maximum activity and regulatory properties.

The International Union of Biochemistry and Molecular Biology (IUBMB) divided enzymes into 6 classes. 

Isoenzymes are enzymes that catalyze identical chemical reactions but are composed of different amino acid sequences. They are sometimes referred to as isozymes. Isoenzymes are produced by different genes. They occur in many tissues throughout the body and are important for different developmental and metabolic processes. Alkaline phosphatase (ALP) and lactate dehydrogenase (LDH) are examples of isoenzymes.

Transferase is an enzyme which transfers a group from one molecule to another molecule. Hexokinase is the enzyme which transfers one phosphate from ATP to glucose and forms glucose 6-phosphate.

Endoenzyme is the cells which function inside the cell. It is also known as intracellular enzymes. It helps in the catalysis of the intracellular metabolic reaction. 

Hydrolases are the enzymes which break large molecules into smaller ones with the help of hydrogen and hydroxyl groups of water molecules, this phenomenon is known as hydrolysis. Amylase is the enzyme produced by the salivary gland and is found in saliva. It breaks starch into glucose. Thus, the correct answer is B.

Ribozymes are also known as ribonucleic acid enzymes. These are RNA molecules which helps in the catalysis of a particular reaction. It was discovered in the year 1982. The RNA can act as both genetic material and can act as a biocatalyst. It acts as a part of ribosome which attaches to the amino acid during protein synthesis. It increases the rate and specificity of peptide bond synthesis and phosphodiester bond. So, the correct answer is option A.

Urease is a nickel-containing metalloprotein which catalyzes the hydrolysis of urea into carbon dioxide and ammonia. Due to the production of ammonia, it increases the production of ammonia. Sumner crystallized an enzyme known as urease and reported that all enzymes are protein. Heliobacter pylori are microbial ureases found in the stomach.

Many enzymes show enzymatic activity only in association with certain non protein substances. Such substances are known as cofactors. Cofactors may be simple ions such as magnesium or potassium ions or complex organic compounds. An organic non-protein cofactor which is easily separable from the enzyme is called coenzyme and the non-protein organic cofactor which is tightly bound to and non-dissociable from the enzyme is termed as prosthetic group. The organic cofactors directly reduce the activation energy and thus form a functional part of active site of enzyme. They act as carriers of chemical groups, atoms or electrons removed from the substrates during reactions.

Certain enzymes are made up of two parts - a protein part of enzyme called apoenzyme and a non-protein part called cofactor. Such enzymes are called conjugated enzymes. The working combination of apoenzyme and cofactor together form the holoenzyme. Organic cofactors are of two types- coenzymes and prosthetic groups. Coenzymes are easily separable organic cofactors while prosthetic groups are non-protein organic cofactors firmly associated with protein part of enzyme called apoenzyme. Heme is iron containing prosthetic group in hemoglobin, myoglobin, cytochrome, catalase and peroxidase. Catalase and peroxidase cause the breakdown of hydrogen peroxide to oxygen and water. Carboxypeptidase requires zinc for its activity.

Ribozymes are also known as ribonucleic acid enzymes. These are RNA molecules which helps in the catalysis of a particular reaction. It was discovered in the year 1982. The RNA can act as both genetic material and can act as a biocatalyst. It acts as a part of ribosome which attaches to the amino acid during protein synthesis. Thomas R. Cech and Sidney Altman discovered catalytic properties of RNA. So, the correct answer is option D.

Hydrolases are biological enzymes that catalyze the hydrolysis of a chemical reaction. They usually divide larger molecules into two smaller molecules. It is a class containing more than 200 enzymes. Some common hydrolases are esterases, proteases, lipases etc.

Diastase is an enzyme that breaks down starch into maltose. It was one of the first enzymes ever discovered and plays a major role in the germination of seeds and brewing.

Peptidyl transferase is the ribozyme component of the ribosome responsible for forming peptide bonds between amino acids during translation.

Based on the type of reaction catalyzed, the international union of biochemist have classified enzymes into six major classes- Oxidoreductase, Transferase, Hydrolase, Lyase, Ligase and Isomerase.
Transferase is the general name for the class of enzymes that enact the transfer of specific functional groups (e.g. a methyl or glycosyl group) from one molecule (called the donor) to another (called the acceptor).

Tyrosinase is a copper-containing enzyme present in plant and animal tissues that catalyzes the production of melanin and other pigments from tyrosine by oxidation, as in the blackening of a peeled or sliced potato exposed to air. In animals it is found inside melanosomes which are synthesised in the skin melanocytes.

Cytochromes are iron-porphyrin or heme proteins discovered by MacCunn. Cytochromes are bound to inner mitochondrial membrane and are primarily responsible for the generation of ATP via mitochondrial electron transport system. Whereas all other cytochromes have iron only, the cytochrome a possesses both iron and copper. With iron it picks up electrons and through copper it hands over electrons to oxygen.

ATPase are a class of enzymes that catalyze the dephosphorylation of ATP into ADP and a free phosphate ion. This dephosphorylation reaction releases energy, which the enzyme harnesses to drive other chemical reactions that would not otherwise occur. This process is widely used in all known forms of life. Such enzymes are integral membrane proteins anchored within biological membranes (plasma membrane), and move solutes across the membrane, typically against their concentration gradient.

Isomerases are the enzymes which catalyse transfer of groups within molecules to yield isomeric bonds. As aldose and ketose sugars are isomers, their interconversion is catalyzed by isomerases.

Certain enzymes carry oxidation reduction reactions. Oxidation is defined as the chemical process which involves loss of electron whereas reduction is the process in which a substrate accepts electron.
An oxygenase is any enzyme that oxidizes a substrate by transferring the oxygen from molecular oxygen O$ _2$ (as in air) to it.

J.B. Sumner isolated ureases from the jack beans and proved enzymes to be proteins, that could be isolated in crystalline form.

The peptidyl transferase is an aminoacyltransferase, it performs the primary enzymatic function of the ribosome, which forms peptide bonds between adjacent amino acids using tRNAs during the translation process of protein biosynthesis. Peptidyl transferase activity is carried out by the ribosome. Peptidyl transferase activity is not mediated by any ribosomal proteins but by ribosomal RNA (rRNA), a ribozyme. 

Lyase are the enzymes which catalyze breakdown reactions without hydrolysis. Lyases are classified as EC 4 in the EC number classification of enzymes. Lyases can be further classified into several subclasses : EC 4.1 includes lyases that cleave carbon-carbon bonds, such as decarboxylases (EC 4.1.1), aldehyde lyases (EC 4.1.2), oxo acid lyases (EC 4.1.3) and others (EC 4.1.99).

Enzymes are biological catalysts which catalyze biological reactions. They do not modify the chemical equilibria in any manner but simply make the attainment of equilibrium faster. Carbonic anhydrase catalyzes reversible reaction between carbon dioxide and water to form carbonic acid. This enzyme is one of the fastest enzyme. It is especially abundant in human erythrocytes.

Enzymes are biological catalysts, which activate various biochemical reactions of a living cell in a highly specific and precise manner. Enzymology is the study of enzymes. The name enzyme was coined by Kuhne in 1878. Pasteur recognised that some microorganisms like yeasts have got a capacity to cause fermentation in wine. In 1897, Buchner discovered that yeast extract could bring about fermentation of grape juice, like the living yeast cells. He also observed that the extract has lost its catalytic activity on boiling. He coined the word zymase for the active principle involved in the fermentation. The substance on which the enzyme acts is called substrate. Enzymes are essentially proteins but all proteins are not enzymes.

Enzymes are biological catalysts which speed up the biological reactions. All metabolic reactions in a cell are catalyzed by enzymes. Almost all enzymes are proteins. There are some nucleic acids that behave like enzymes. These are called ribozymes. Ribozymes are molecules of ribonucleic acid with catalytic activity.

Endonucleases hydrolyse internal phosphodiester bonds in a polynucleotide chain. Function of nucleases is to break phosphodiester bond. A nuclease is an enzyme capable of cleaving the phosphodiester bonds between the nucleotide subunits of nucleic acids. Nucleases are usually further divided into endonucleases and exonucleases, although some of the enzymes may fall in both categories. 

Enzymes are biological catalysts, which activate various biochemical reactions of a living cell in a highly specific and precise manner. Enzymology is the study of enzymes. The name enzyme was coined by Kuhne in 1878. Pasteur recognised that some microorganisms like yeasts have got a capacity to cause fermentation in wine. In 1897, Buchner discovered that yeast extract could bring about fermentation of grape juice, like the living yeast cells. He also observed that the extract has lost its catalytic activity on boiling. He coined the word zymase for the active principle involved in the fermentation. The substance on which the enzyme acts is called substrate. Enzymes are essentially proteins but all proteins are not enzymes.

• In 1897, Eduard Buchner discovered that yeast extracts could ferment sugar to alcohol, proving that fermentation was promoted by molecules that continued to function when removed from cells. Frederick W. Khne called these molecules like enzymes.
  Hence, the correct option is B.

The enzyme that cause chromosomal breaks are DNase. A deoxyribonuclease or DNase, is any enzyme that catalyzes the hydrolytic cleavage of phosphodiester linkages in the DNA backbone, thus degrading DNA. Deoxyribonucleases are one type of nuclease, a generic term for enzymes capable of hydrolising phosphodiester bonds that link nucleotides.

Enzymes are biological catalysts, which activate various biochemical reactions of a living cell in a highly specific and precise manner. Enzymology is the study of enzymes. The name enzyme was coined by Kuhne in 1878. Pasteur recognised that some microorganisms like yeasts have got a capacity to cause fermentation in wine. In 1897, Buchner discovered that yeast extract could bring about fermentation of grape juice, like the living yeast cells. He also observed that the extract has lost its catalytic activity on boiling. He coined the word zymase for the active principle involved in the fermentation. The substance on which the enzyme acts is called substrate. Enzymes are essentially proteins but all proteins are not enzymes.

Buchner coined the term zymase for the complex of biocatalysts extracted from yeast and taking part in alcoholic fermentation. Pasteur is responsible for the process of pasteurization and Kuhne is best known today for coining the word enzyme.

Rennin is a protease found in rennet. It is produced by newborn ruminant animals in the lining of the fourth stomach to curdle the milk they ingest, allowing a longer residence in the bowels and better absorption. It is widely used in the production of cheese.

Dehydrogenases are the enzymes which catalyze oxidation-reduction reactions by addition or removal of electrons. These reactions are used to synthesize reduced coenzymes like NADH$ _2$ and FADH$ _2$. For example phosphoglyceraldehyde dehydrogenase.

Ribozymes or RNA enzymes are catalytic RNA molecules. The first ribozyme discovered was self splicing group I intron. The second catalytic RNA was RNAase P which separates tRNA from hn RNA at their 5' ends. Peptidyl transferase involved in translation of proteins is also catalytic RNA. Telomerase is a ribonulceoprotein  enzyme. It is involved in replication of terminal DNA or telomeres.

A restriction enzyme or restriction endonuclease or molecular scissors is an enzyme used in genetic engineering that splices DNA at or near specific recognition nucleotide sequences, known as restriction sites. Thus, the correct answer is option C.

Enzymes are biological catalysts which catalyse the biochemical reactions in living systems. Majority of enzymes are proteins. A small minority of enzymes are catalytic RNA molecules. These catalytic RNA molecules are called ribozymes. These catalytic RNA molecules catalyze reactions like splicing of introns during processing of RNA in eukaryotic mRNA.

Co-enzymes tightly or covalently bonded to enzymes are called prosthetic groups, e.g., pyridoxal phosphate, heme, biotin. Heme is a prosthetic group containing ferrous ion. It is important for a number of biologically important hemoproteins such as myoglobin, cytochrome oxidase, catalase and peroxidase. Thus, the correct answer is option E.

Prosthetic groups are tightly bound cofactors. Peptidase enzymes hydrolyze peptide bonds. Peptidase enzymes require manganese ion for their activity as prosthetic group.

Some enzymes require metal ions for their activity. Tyrosinase is a copper containing enzyme that catalyzes the production of melanin and other pigments.

Hydrolase enzymes break large molecules into small molecules with the help of hydrogen and hydroxyl group of water molecules. The phenomenon is known as hydrolysis. Digestive enzymes in our body help to break down macromolecules of food into smaller molecules by the process of hydrolysis. So, digestive enzymes belong to the class Hydrolases. Thus, the correct option is B.

Simple enzymes consist of only proteins and catalyze their substrate specific reactions. Urease is an enzyme which is only made up of protein and it functions to catalyze the hydrolysis of urea which results in the formation of ammonia and carbon dioxide.

Starch is used as food reserves in plants. It is a polymer of glucose. It is formed by the attachment of glucose unit by glycosidic bonds. The basic formula of starch is (C$ _6$H$ _{10}$O$ _5$)n. 

Lyase is the enzyme by which the chemical bonds are broken down by the process other than hydrolysis and oxidation. It allows the formation of new bond. 

Transferase is an enzyme that transfers a specific functional groups from one molecule to another. 

Hydrolase is a class of enzyme which act as biochemical catalysts that use water to break chemical bonds.

Alcalase is a protease commonly used in detergents to break down protein-based stains.

Dehydrogenase is an enzyme which participates in the oxidoreductase reaction by using an electron acceptor. It is involved in the transfer of electrons because it oxidizes a substrate by reducing it which means it transfers the electron from the substrate to an electron acceptor. Succinate dehydrogenase is an enzyme which is present in the inner mitochondrial membrane. It catalyzes the oxidation of succinate to fumarate.

Inducible enzymes are synthesized only in the presence of their specific substrate, such as the enzymes of the lac operon in the presence of lactose.

Lyases is an enzyme which catalyses the joining of specified molecules or groups by a double bond. Lyases catalyze reactions where functional groups are added to break double bonds in molecules or the reverse where double bonds are formed by the removal of functional groups.
So, the correct answer is option B.

In enzymology, turnover number is the number of substrate molecules converted to products in a given unit of time on a single enzyme molecule when the enzyme is saturated with substrate. The enzyme catalase has highest turnover number value of 40,000,000 (per second per molecule of enzyme), followed by Carbonic anhydrase 400,000 (per second per molecule of enzyme), followed by acetylcholinesterase 140,000 (per second per molecule of enzyme), followed by $\beta$-lactamase 2000 (per second per molecule of enzyme).

The scientists listed in question had made some of the most outstanding contributions.
Pasteur discovered fermentation.  The biochemical process carried out by yeast which results in fermented products like beer and butter milk.
The first commercial standardized rennet was introduced by Chr Hansen in 1874. At that time, rudimentary methods were used to extract animal rennet from calves or adult bovine stomachs.
Diastase was the first enzyme discovered. It was extracted from malt solution in 1833 by Anselme Payen and Jean-Franois Persoz, chemists at a French sugar factory.
Waksman was awarded the Nobel Prize in Physiology or Medicine in recognition for his discovery of streptomycin, the first antibiotic active against tuberculosis.

The EC number 4.2.1.7 is assigned to the enzyme named altronate dehydratase or D-altronate hydro-lyase. This enzyme catalyses the dehydration of D-altronate and results in the formation of 2-dehydroxy-3-deoxy-D-gluconate and water. 

Phosphodiesterase is a hydrolase enzyme. So, it's EC number is 3.

Natural source of subtilin is bacteria Bacillus subtilis. Subtilisins are proteolytic enzymes mainly used in detergents and house hold cleaning products to remove proteinaceous deposits and stains.

Histone proteins are rich in basic amino acids and form the core around which the DNA is wound giving rise to nucleosome particles. DNA is wound around histones because basic amino acids are positively charged at physiological pH which facilitates winding of acidic or negatively charged DNA. Neutralization of positive charge, on basic amino acids of histone proteins, by chemical processes like reversible acetylation will lead to neutralization of attractive force between nucleosome core and DNA molecule. This will in turn lead to transcriptional activation (histone proteins are acetylated) and after transcription once again the histone proteins will be deacetylated restoring there positive charge, thus facilitating the tight binding between (negatively charged) DNA and (positively charged) histone core. Apart from reversible acetylation, histone proteins also undergo a number of other chemical modifications. Thus, acting as modulators for DNA metabolism.

in 1897, Eduard Buchner discovered that yeast extracts could ferment sugar to alcohol, proving that fermentation was promoted by molecules that continued to function when removed from cells. Frederick W. Khne called these molecules as enzymes. The isolation and crystallization of urease by James Sumner, in 1926, provided a breakthrough in early enzyme studies. Sumner found that urease crystals consisted entirely of protein, and he postulated that all enzymes are proteins. In the absence of other examples, this idea remained controversial for some time. Only in the 1930s, was Sumners conclusion widely accepted, after John Northrop and Moses Kunitz crystallized pepsin, trypsin, and other digestive enzymes and found them also to be proteins.

Isoenzymes are an unique example in which the same reaction may be catalyzed by two or more different molecular forms of an enzyme. The multiple forms, called isozymes or isoenzymes, may occur in the same species, in the same tissue, or even in the same cell. The different forms of the enzyme generally differ in kinetic or regulatory properties, in the cofactor they use (NADH or NADPH for dehydrogenase isozymes, for example), or in their subcellular distribution (soluble or membrane-bound). Isozymes may have similar, but not identical, amino acid sequences, and in many cases they clearly share a common evolutionary origin. One of the first enzymes found to have isozymes was lactate dehydrogenase (LDH), which, in vertebrate tissues, exists as at least five different isozymes separable by electrophoresis. However, isoenzymes follow the same general mechanism of enzyme action, i.e., decreasing the activation energy of substrates for a reaction.

Gastrin is a peptide hormone, which is secreted by the gastric glands in the stomach wall. The gastrin stimulates secretion of gastric juice rich in pepsin and hydrochloric acid. The stimulation for secretion of gastrin is presence of peptides derived from dietary proteins.

Enzymes are biological catalysts. The multitude of biochemical reactions that make cellular metabolism possible are due to enzymes. The isolation and crystallization of urease by James Sumner in 1926 provided a breakthrough in early enzyme studies. Sumner found that urease crystals consisted entirely of protein, and he postulated that all enzymes are proteins. In the absence of other examples, this idea remained controversial for some time. Only in the1930s, was Sumners conclusion widely accepted, after John Northrop and Moses Kunitz crystallized pepsin, trypsin, and other digestive enzymes and found them also to be proteins.

An amylase is an enzyme that catalyses the hydrolysis of starch into sugars. A hydrolase or hydrolytic enzyme is an enzyme that catalyzes the hydrolysis of a chemical bond.
So, the correct answer is option C.

The non-protein component or prosthetic group along with the protein component or apoenzyme is called the holoenzyme. The prosthetic group may be metal ion or a co-enzyme that may be firmly or losely bound to the enzyme.
So, the correct answer is option B.

Enzymes are biocatalyst that affects the rate of biochemical reactions they generally have the same pH and temperature Optima at which they work efficiently. 

A lysosome is a membrane-bound organelle found in nearly all animal cells. They are spherical vesicles which contain hydrolytic enzymes that can break down many kinds of biomolecules.
So, the correct answer is option C.

Most of the enzymes are large protein molecules except for a small category of catalytic RNA molecules. The catalytic RNA molecules are called Ribozymes. Ribozymes play an important role in intron splicing and other reactions during processing of RNA. The ribozymes are an important example of self catalytic (RNA) molecules, i.e., one type of RNA (ribozyme) acting on another type of RNA (like mRNA). Some of the introns are self splicing which catalyze their own splicing.

Lysosomes are membrane-bound vesicles that contain digestive enzymes, such as glycosidases, proteases and sulfatases. Lysosomal enzymes are synthesized in the endoplasmic reticulum (ER), are transported to the Golgi apparatus, and are tagged for lysosomes by the addition of mannose-6-phosphate label. Digestive enzymes are not found in chloroplast and mitochondria. 

Ligases are the enzymes which catalyze joining together of two DNA segments. Lyases catalyze the breaking of chemical bonds without hydrolysis while hydrolases catalyze hydrolytic cleavage of bonds. Isomerases catalyze interconversion of optical, geometrical or positional isomers of a particular enzyme.

Endopeptidase are the proteolytic enzymes which cleave the peptide chain at internal locations. They break peptide bonds of non terminal amino acids (i.e. within the molecule), in contrast to exopeptidases, which break peptide bonds from their end-pieces. One example is papain obtained from unripe papaya.

Restriction endonuclease are a part of cellular defense system in bacteria. These enzymes cleave or restrict external or exogenous DNA. A type of these enzymes act on specific palindromic sequences which they recognize.

Enzymes are simple if they are made up of only proteins, e.g., pepsin, amylase, etc., while conjugate enzymes have an additional non-protein cofactor, e.g., dehydrogenase enzymes. The cofactor can be organic or inorganic. Loosely attached organic cofactor are called coenzymes, e.g., NAD, FAD etc., while firmly attached one is prosthetic group, e.g., haeme, biotin etc.