enzymes2-140121084121-phpapp02 (1).pdf_20241225_084326_0000.pdf
- 1. . DR : OMNIA ABDO Instructor in clinical chemistry course at Plasma Company Instructor in microbiology & immunology course in plasma company Enzymes
- 2. CHEMISTRY
- 3. Introduction Enzymes are biological catalysts that speed uptherateofthebiochemicalreaction. Most enzymes are three dimensional globular proteins(tertiaryandquaternarystructure). Some special RNA species also act as enzymes and are called Ribozymes e.g. hammerheadribozyme. Hammerhead enzyme
- 4. STRUCTURE OF ENZYMES The active site of an enzyme is the region that binds substrates, co-factors and prosthetic groups and contains residue that helps to hold the substrate. Active sites generally occupy less than 5% of the total surface area of enzyme. Active site has a specific shape due to tertiary structure of protein. A change in the shape of protein affects the shape of active site and function of the enzyme.
- 5. ACTIVE SITE o . Active site can be further divided into: It chooses the substrate and binds it to active site It performs the catalytic action of enzyme. Binding Site Active Site Catalytic Site
- 6. C - O FACTORS o o Organic co-factors Inorganic cofactors Co-factor is the non protein molecule which carries out chemical reactions that can not be performed by standard 20 amino acids. Co-factors are of two types:
- 7. An enzyme with it‟s co-factor removed is designated as apoenzyme. The complete complex of a protein with all necessary small organic molecules, metal ions and other components is termed as holoenzyme of holoprotein. Types of co-factors Continued…
- 8. SUBSTRATE The reactant in biochemical reaction is termed as substrate. When a substrate binds to an enzyme it forms an enzyme- substrate complex. Enzyme Joins Substrate
- 9. SITES OF ENZYME SYNTHESIS o o o Enzymes are synthesized by ribosomes which are attached to the rough endoplasmic reticulum. Information for the synthesis of enzyme is carried by DNA. Amino acids are bonded together to form specific enzyme according to the DNA‟s codes.
- 10. INTRACELLULAR AND EXTRACELLULAR ENZYMES o o Intracellular enzymes are synthesized and retained in the cell for the use of cell itself. They are found in the cytoplasm, nucleus, mitochondria and chloroplast. Example : Oxydoreductase catalyses biological oxidation. Enzymes involved in reduction in the mitochondria. Extracellular enzymes are synthesized in the cell but secreted from the cell to work externally. Example : Digestive enzyme produced by the pancreas, are not used by the cells in the pancreas but are transported to the duodenum. o
- 11. CHARACTERISTICS Enzymes speed up the reaction by lowering the activation energy of the reaction. Their presence does not effect the nature and properties of end product. They are highly specific in their action that is each enzyme can catalyze one kind of substrate. Small amount of enzymes can accelerate chemical reactions. Enzymes are sensitive to change in pH, temperature and substrate concentration.
- 12. EXAMPLES substrate enzymes products lactose maltose cellulose lipid starch protein lactase maltase cellulase lipase amylase protease glucose + galactose Glucose Glucose Glycerol + fatty acid Maltose Peptides + polypeptide
- 13. CLASSIFICATION
- 14. CLASSIFICATION OF ENZYMES A systematic classification of enzymes has been developed by International Enzyme Commission. This classification is based on the type of reactions catalyzed by enzymes. Each class is further divided into sub classes, sub sub-classes and so on, to describe the huge number of different enzyme- catalyzed reactions. There are six major classes.
- 15. Ligases Lysases Isomerases ENZYME CLASS Oxidoreductases Transferases Hydrolases REACTION TYPE Reduction-oxidation (redox) Move chemical group Hydrolysis; bond cleavage with transfer of functional group of water Non-hydrolytic bond cleavage Intramolecular group transfer (isomerization) Synthesis of new covalent bond between substrates, using ATP hydrolysis EXAMPLES Lactate dehydrogenase Hexokinase Lysozyme Fumarase Triose phosphate isomerase RNA polymerase Continued…….. Classification of enzymes
- 17. MECHANISM OF ENZYME ACTION The catalytic efficiency of perspectives: enzymes is explained by two Thermodynamic changes Processes at the active site
- 18. THERMODYNAMIC CHANGES All chemical reactions have energy barriers between reactants and products. The difference in transitional state and substrate is called activational barrier.
- 19. ENZYMES KINETICS
- 20. INTRODUCTION “It is a branch of biochemistry in which we study the rate of enzyme catalyzed reactions.” Kinetic analysis reveals the number and order of the individual stepsbywhichenzymestransformsubstrateintoproducts Studying an enzyme's kinetics in this way can reveal the role in metabolism, how its activity is controlled, and how a drug or anagonistmightinhibittheenzyme catalytic mechanism of that enzyme, its
- 21. ENZYMES LOWER THE ACTIVATION ENERGY OF A REACTION Final energy state of products Initial energy state of substrates Activation energy of enzyme catalysed reaction Activation energy of uncatalysed reactions Progress of reaction (time) Energy levels of molecules
- 22. FACTORS AFFECTING RATE OF ENZYME CATALYZED REACTIONS Temperature Hydrogen ion concentration(pH) Substrate concentration
- 23. EFFECT OF TEMPERATURE Raising the temperature increases the rate of enzyme catalyzed reaction by increasing kinetic energy of reacting molecules. Enzymes work maximum over a particular temperature known as optimum temperature. Enzymes for humans generally exhibit stability temperature up to 35-45 ᵒC. The temperature coefficient is a factor Q₁₀by which the rate of biological processes increases for a 10 ᵒC increase in temperature. For most biological processes Q₁₀= 2. However some times heat energy can also increase kinetic energy to a point that exceed the energy barrier which results in denaturing of enzymes.
- 24. Rate of Reaction Temperature o <5oC -inactive 5-40oC Increase in Activity 0 10 20 30 40 50 60 40C -denatures
- 25. EFFECT OF PH Rate of almost all enzymes catalyzed reactions depends on pH Most enzymes exhibit optimal activity at pH value between 5 and9 High or low pH value than optimum value will cause ionization of enzyme which result in denaturation of enzyme
- 26. P AFFECTS THE FORMATION OF HYDROGEN BONDS AND SULPHUR BRIDGES IN PROTEINSAND SOAFFECTS SHAPE. H pepsin 8 10 Acidic 2 4 6 pH trypsin arginase Basic Rate of Reaction (M)
- 29. ENZYME SPECIFICITY Enzymes are highly specific in nature, interacting with one or few substrates and catalyzing only one type of chemical reaction. Substrate specificity is due to complete fitting of active site and substrate .