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- 2. Enzymes Biological catalysts, which speed up the reaction without being consumed. Without enzymes, many of these reactions would not take place at a perceptible rate. Enzymes accelerate almost all biochemical process, replication, repair, growth, digestion etc.
- 3. Enzymes For survival Organism must be able to self-replicate It must be able to catalyze chemical reactions efficiently and selectively
- 4. Enzymes Vs. Catalysts 1- Enzymes have extraordinary catalytic power, often far greater than that of synthetic or inorganic catalysts.
- 5. 2- They have a high degree of specificity for their substrates 3- Function in aqueous solutions 4- Require very mild conditions of temperature and pH.
- 6. Enzymes are important 1- Enzymes are central to every biochemical process.
- 8. 2- In some diseases, especially inheritable genetic disorders, there may be a deficiency or even a total absence of one or more enzymes.
- 11. 3- Other disease conditions may be caused by excessive activity of an enzyme.
- 12. 4- Measurements of the activities of enzymes in blood plasma, erythrocytes, or tissue samples are important in diagnosing certain illnesses.
- 13. 5- Many drugs act through interactions with enzymes.
- 14. 6- Enzymes are important in industries, food, textile, agriculture etc. Pectinases
- 15. In the 1850s, Louis Pasteur concluded that fermentation of sugar into alcohol by yeast is catalyzed by ferments. He postulated that these ferments were inseparable from the structure of living yeast cells; this view, called vitalism, prevailed for decades. Enzymes: History
- 16. 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 even removed from cells.
- 18. Frederick W. K端hne later gave the name enzymes (from the Greek enzymos, leavened) to the molecules detected by Buchner. The isolation and crystallization of urease by James Sumner in 1926 was a breakthrough in early enzyme studies. Sumner found that urease crystals consisted entirely of protein, and he postulated that all enzymes are proteins.
- 19. With the exception of a small group of catalytic RNA molecules all enzymes are proteins. The catalytic activity of a protein depends on the integrity of its native conformation. If an enzyme is denatured or dissociated into its subunits, catalytic activity is usually lost. Most Enzymes are proteins
- 20. Thus the primary, secondary, tertiary, and quaternary structures of protein enzymes are essential to their catalytic activity.
- 21. One part of an enzyme, the active site, is particularly important. Active site is divided into two sites There are some amino acid residues that form temporary bonds with the substrate (binding site) and residues that catalyse a reaction of that substrate (catalytic site) Active site of enzyme
- 22. The shape and the chemical environment inside the active site permits a chemical reaction to proceed more easily.
- 23. The protein portion of an enzyme is called apoenzyme. Some enzymes require an additional non-protein part to perform their activities. The non-protein parts are called cofactor (metal ions). Non-protein partners of enzymes
- 24. If the non protein part is a complex organic or metallo-organic molecule it is called as coenzyme. A coenzyme or metal ion that is very tightly or even covalently bound to the enzyme protein is called a prosthetic group. A complete, catalytically active enzyme together with its bound coenzyme and/or metal ions is called a holoenzyme.
- 27. Many enzymes have been named by adding the suffix -ase to the name of their substrate or to a word or phrase describing their activity. Other enzymes were named by their discoverers for a broad function, before the specific reaction catalyzed was known. This sort of classification was quite ambiguous as the same enzyme has two or more names, or two different enzymes have the same name Enzymes Classifications
- 28. International Union of Biochemistry and Molecular Biology classified enzymes into six classes
- 29. . 1) Oxidoreductases: This is a very broad class of enzymes that catalyze the many oxidation-reduction reactions found in biochemical pathways. Oxidoreductases catalyze reactions in which at least one substrate gains electrons, becoming reduced, and another loses electrons, becoming oxidized.
- 31. 2) Transferases: This class of enzymes catalyze the transfer of a specific functional group between molecules. Important subsets of transferases include a) Kinases transfer phosphate groups, usually from ATP to another molecule (such as hexokinase and glucokinase, that phosphorylate glucose and protein kinases that phosphorylate protein hydroyxl groups), b) Aminotransferases transfer amino groups that are important in amino acid metabolism, c) Acyltransferases transfer fatty acyl groups d) Glycosyltransferases, which transfer carbohydrate residues.
- 35. 3) Hydrolases: Enzymes responsible to break the bond by using water molecule. Hydrolysis reactions refer to the cleavage of bonds by the addition of a water molecule.
- 37. 4) Lyases: Lyases are the enzymes which cleave C-C, C-O, C-N or C-S bond leaving a double bond or addition of groups to double bond. Examples include aldolases (such as fructose diphosphate aldolase, which is involved in glycolysis) and thiolases (such as b-ketoacyl-CoA thiolase involved in the breakdown of fatty acids).
- 39. 5) Isomerases: Transfer of groups within molecule to generate isomeric forms. For example, triose phosphate isomerase catalyzes the interconversion between dihydroxyacetone phosphate and D-glyceraldehyde 3- phosphate, which is essential for continuing glycolysis following splitting of six carbon sugars into two three carbon sugars by fructose diphosphate aldolase
- 42. 6) Ligases: Ligases are involved in synthesizing bonds between carbon atoms and carbon, nitrogen, oxygen or sulfur atoms in reactions that are coupled to the cleavage of the high energy phosphate of ATP or another nucleotide. Pyruvate carboxylase, a key enzyme in gluconeogenesis, is one important ligase in metabolism.
- 44. Each enzyme has specific EC number The nomenclature was determined by the Enzyme Commission in 1961 (with the latest update having occurred in 1992), hence all enzymes are assigned an EC number.