ENZYME: an essential catalyst There are two fundamental conditions for life.

1. ENZYME: an essential catalyst There are two fundamental conditions for life. First, the living entity must be able to self-replicate; Second, the organism must be able to catalyze chemical Reactions efficiently and selectively. Living systems make use of energy from the environment. Many of us, for example, consume substantial amounts of sucrose—common table sugar—as a kind of fuel, whether in the form of sweetened foods and drinks or as sugar itself. The conversion of sucrose to CO2 and H2O in the presence of oxygen is a highly exergonic process, releasing free energy that we can use to think, move, taste, and see. However, a bag of sugar can remain on the shelf for years without any obvious conversion to CO2 and H2O. Although this chemical process is thermodynamically favorable, it is very slow! Yet when sucrose is consumed by a human (or almost any other organism), it releases its chemical energy in seconds. The difference is catalysis. Without catalysis, chemical reactions such as sucrose oxidation could not occur on a useful time scale, and thus could not sustain life.

2. HISTORY As early as the late 17th and early 18th centuries, the digestion of meat by stomach secretions and the conversion of starch to sugars by plant extracts and saliva were known. However, the mechanism by which this occurred had not been identified. 1833, French chemist AnselmePayen discovered the first enzyme, diastase. 1850 A few decades later, when studying the fermentation of sugar to alcohol by yeast, Louis Pasteur came to the conclusion that this fermentation was catalyzed by a vital force contained within the yeast cells called "ferments", which were thought to function only within living organisms. He wrote that "alcoholic fermentation is an act correlated with the life and organization of the yeast cells, not with the death or putrefaction of the cells. 1877, German physiologist Wilhelm Kühne (1837–1900) first used the term enzyme, which comes from Greek ενζυμον, "in leaven". The word enzyme was used later to refer to nonliving substances such as pepsin, and the word ferment was used to refer to chemical activity produced by living organisms. In 1876, he discovered the protein-digesting enzyme trypsin.

3. 1897, Eduard Buchner submitted his first paper on the ability of yeast extracts that lacked any living yeast cells to ferment sugar. In a series of experiments at the University of Berlin, he found that the sugar was fermented even when there were no living yeast cells in the mixture. He named the enzyme that brought about the fermentation of sucrose "zymase". In 1907, he received the Nobel Prize in Chemistry "for his biochemical research and his discovery of cell-free fermentation". Following Buchner's example, enzymes are usually named according to the reaction they carry out. Typically, to generate the name of an enzyme, the suffix -ase is added to the name of its substrate (e.g., lactase is the enzyme that cleaves lactose) or the type of reaction (e.g., DNA polymerase forms DNA polymers). 1926, James B. Sumner showed that the enzyme urease was a pure protein and crystallized it; Sumner did likewise for the enzyme catalase in 1937. The conclusion that pure proteins can be enzymes was definitively proved by John Howard Northrop and Wendell Meredith Stanley, who worked on the digestive enzymes pepsin (1930), trypsin and chymotrypsin. These three scientists were awarded the 1946 Nobel Prize in Chemistry.

4. During this period J. B. S. Haldane wrote a treatise entitled Enzymes. Although the molecular nature of enzymes was not yet fully appreciated, Haldane made the remarkable suggestion that weak bonding interactions between an enzyme and its substrate might be used to catalyze a reaction. This insight lies at the heart of our current understanding of enzymatic catalysis. 1964 This discovery that enzymes could be crystallized eventually allowed their structures to be solved by x-ray crystallography. This was first done for lysozyme, an enzyme found in tears, saliva and egg whites that digests the coating of some bacteria; the structure was solved by a group led by David Chilton Phillips and published in 1965. This high-resolution structure of lysozyme marked the beginning of the field of structural biology and the effort to understand how enzymes work at an atomic level.

5. General Characteristics of Enzymes Enzymes are central to every biochemical process. Acting in organized sequences, they catalyze the hundreds of stepwise reactions that degrade nutrient molecules, conserve and transform chemical energy, and make biological macromolecules from simple precursors. • Organic Nature: Enzymes are in general globular proteins and range from just 62 amino acid residues in size, for the monomer of 4-oxalocrotonate tautomerase, to over 2,500 residues in the animal fatty acid synthase. A small number of RNA-based biological catalysts exist, with the most common being the ribosome; these are referred to as either RNA-enzymes or ribozymes. The activities of enzymes are determined by their three-dimensional structure. However, although structure does determine function, predicting a novel enzyme's activity just from its structure is a very difficult problem that has not yet been solved. 2. Catalytic Efficiency: Catalyst - a substance that speeds up the rate of a reactionwithout being changed itself by lowering the activation energy of a reaction. The same reaction would eventually occur, but not at a rate fast enough for survival. For example, the hydrolysis of protein in our diet would occur without a catalyst, but not fast enough to meet the body’s requirements for amino acids.

6. 3. Specificity: Enzymes are usually very specific as to which reactions they catalyze and the substrates that are involved in these reactions. Complementary shape, charge and hydrophilic/hydrophobic characteristics of enzymes and substrates are responsible for this specificity. Enzymes can also show impressive levels of stereospecificity, regioselectivity and chemoselectivity. Some of the enzymes showing the highest specificity and accuracy are involved in the copying and expression of the genome. These enzymes have "proof-reading" mechanisms. Here, an enzyme such as DNA polymerase catalyzes a reaction in a first step and then checks that the product is correct in a second step. This two-step process results in average error rates of less than 1 error in 100 million reactions in high-fidelity mammalian polymerases. Similar proofreading mechanisms are also found in RNA polymerase and aminoacyl tRNA synthetases. 4. Enzyme regulation: Various ways

7. 5. Enzyme production : induction/inhibition Transcription and translation of enzyme genes can be enhanced or diminished by a cell in response to changes in the cell's environment. This form of gene regulation is called enzyme induction and inhibition. For example, bacteria may become resistant to antibiotics such as penicillin because enzymes called beta-lactamases are induced that hydrolyze the crucial beta-lactam ring within the penicillin molecule. Another example are enzymes in the liver called cytochrome P450 oxidases, which are important in drug metabolism. 6. Enzymes can be compartmentalized, with different metabolic pathways occurring in different cellular compartments. For example, fatty acids are synthesized by one set of enzymes in the cytosol, endoplasmic reticulum and the Golgi apparatus and used by a different set of enzymes as a source of energy in the mitochondrion, through β-oxidation. 7. Disease & Enzyme: Since the tight control of enzyme activity is essential for homeostasis, any malfunction (mutation, overproduction, underproduction or deletion) of a single critical enzyme can lead to a genetic disease. The importance of enzymes is shown by the fact that a lethal illness can be caused by the malfunction of just one type of enzyme out of the thousands of types present in our bodies.

8. The International Union of Biochemistry and Molecular Biology (IUBMB) Founded in 1955 - unites biochemists and molecular biologists in 77 countries that belong to the Union as an Adhering Body or Associate Adhering Body which is represented as a biochemical society, a national research council or an academy of sciences. The Union is devoted to promoting research and education in biochemistry and molecular biology throughout the world and gives particular attention to areas where the subject is still in its early development. The IUBMB is one of 26 Scientific Unions affiliated with the International Council of Science (ICSU), an umbrella organization for scientists worldwide. ICSU was created in 1931 to encourage international scientific activity, to affirm the rights of scientists without regard to race, religion, political philosophy, ethnic origin, sex or language, to join in international scientific affairs for the benefit of mankind. The IUBMB has been a member of ICSU since 1955 (until 1991 as IUB).

9. IUBMB Activities • The IUBMB is engaged in variety of activities. For details follow the links to the left, and above (for Publications): • Every three years, the world's biochemists come together at the IUBMB International Congress of Biochemistry and Molecular Biology. • Travel awards and a special two-day pre-Congress programme for young scientists, called Young Scientists Program (YSP) is a special feature attached to this event. • IUBMB Conferences take place in the years between IUBMB Congresses. They enhance the visibility of IUBMB in regions of significant or major biochemical activity and present opportunities for review of advances in a limited number of topic areas. • A new activity is the IUBMB Special Meeting, a more focused meeting than the conference type. • IUBMB sponsors international Symposia and Workshops worldwide on focused topics. • The Wood-Whelan Fellowships provide short-term fellowships for younger biochemists to travel to other laboratories to undertake research that cannot be done in their own laboratories. • Reaching individual biochemists is also the purpose of another very important function of the IUBMB, that of publishing journals containing news, reviews, information, original research and also maps and nomenclature. • The IUBMB Jubilee Lectures have been established to commemorate the 50th anniversary of the first International Congress of Biochemistry held in Cambridge, UK in 1949, at which steps were taken that led to formation of IUB (IUBMB since 1991)

10. The International Union of Pure and Applied Chemistry (IUPAC) and the International Union of Biochemistry and Molecular Biology (IUBMB) have established the IUPAC-IUBMB Joint Commission on Biochemical Nomenclature (JCBN) and the Nomenclature Committee of the International Union of Biochemistry and Molecular Biology (NC-IUBMB). The purpose of the committees is to facilitate communication of biochemical information by encouraging scientists to use generally understood terminology. The committees seek advice from experts in the diverse fields of biochemistry about matters where communication is difficult because of inconsistent practices.

11. Procedures for establishing new recommendations The initial recommendations for any topic are always prepared by experts in the subject area, but are subsequently studied by the nomenclature committees in an effort to harmonize them with recommendations in related areas of biochemistry, or indeed in chemistry and other disciplines. Although this step often appears unnecessary to experts in a restricted area of the subject, its importance emerges when one attempts to present information on a broader scale or to a broader audience. Recommendations of the nomenclature committees are published in the primary research literature. All JCBN recommendations are published in Pure and Applied Chemistry, and all JCBN and NC-IUBMB recommendations are currently published in the European Journal of Biochemistry, by courtesy of FEBS. Many documents appear also in other journals, and any journal wishing to republish a document can normally obtain reproduction-quality proofs from the European Journal of Biochemistry, to avoid the need for re-setting.

12. The different kinds of enzymes are named in different ways • Most often enzymes are named by adding a suffix 'ase' to the root word of the substrate. For example, Lipase (fat hydrolysing enzyme), Sucrase (breaking down sucrose). • Sometimes the enzymes are named on the basis of the reaction that they catalyse. For example, Polymerase (aids in polymerisation), Dehydrogenase (removal of H atoms). • Some enzymes have been named based on the source from which they were first identified. For example, Papayin from papaya. • The names of some enzymes ends with an 'in' indicating that they are basically proteins. For example, Pepsin, Trypsin etc.

13. Enzyme Nomenclature • An enzyme's name is often derived from its substrate or the chemical reaction it catalyzes, with the word ending in -ase. Examples are lactase, alcohol dehydrogenase and DNA polymerase. • This may result in different enzymes, called isozymes, with the same function having the same basic name. Isoenzymes have a different amino acid sequence and might be distinguished by their optimal pH, kinetic properties or immunologically. • Isoenzyme and isozyme are homologous proteins. • Furthermore, the normal physiological reaction an enzyme catalyzes may not be the same as under artificial conditions. This can result in the same enzyme being identified with two different names. For example, glucose isomerase, which is used industrially to convert glucose into the sweetener fructose, is a xylose isomerase in vivo (within the body). • The International Union of Biochemistry and Molecular Biology have developed a nomenclature for enzymes, the EC numbers; each enzyme is described by a sequence of four numbers preceded by "EC". The first number broadly classifies the enzyme based on its mechanism.

14. EC 1 Oxidoreductases: catalyze oxidation/reduction reactions • EC 2 Transferases: transfer a functional group (e.g. a methyl or phosphate group) • EC 3 Hydrolases: catalyze the hydrolysis of various bonds • EC 4 Lyases: cleave various bonds by means other than hydrolysis and oxidation • EC 5 Isomerases: catalyze isomerization changes within a single molecule • EC 6 Ligases: join two molecules with covalent bonds • According to the naming conventions, enzymes are generally classified into six main family classes and many sub-family classes. • Some web-servers, e.g., EzyPred and bioinformatics tools have been developed to predict which main family class and sub-family class an enzyme molecule belongs to according to its sequence information alone.

15. Format of number • Scheme for the classification of enzymes and the generation of EC numbers • The first Enzyme Commission, in its report in 1961, devised a system for classification of enzymes that also serves as a basis for assigning code numbers to them. • These code numbers, prefixed by EC, which are now widely in use, contain four elements separated by points, with the following meaning: • the first number shows to which of the six main divisions (classes) the enzyme belongs, • (ii) the second figure indicates the subclass, • (iii) the third figure gives the sub-subclass, • (iv) the fourth figure is the serial number of the enzyme in its sub-subclass.

16. For example, Tripeptide aminopeptidases have the code "EC 3.4.11.4", whose components indicate the following groups of enzymes: EC 3 enzymes are hydrolases (enzymes that use water to break up some other molecule ) catalyzed reaction EC 3.4 are hydrolases that act on peptide bonds- specific chemical interaction EC 3.4.11 are those hydrolases that cleave off the amino-terminal amino acid from a polypeptide-regiospecificity EC 3.4.11.4 are those that cleave off the amino-terminal end from a tripeptide