Enzymes.pptx
- 1. BY Assist. Prof. Dr.Berciyal Golda. P VICAS
- 2. INTRODUCTION Enzymes are proteins that act as biological catalysts (biocatalysts). Catalysts accelerate chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products.
- 3. •The biological processes that occur within all living organisms are chemical reactions, and most are regulated by enzymes. •Without enzymes, many of these reactions would not take place at a perceptible rate. •Enzymes catalyze all aspects of cell metabolism. This includes the digestion of food, in which large nutrient molecules (such as proteins, carbohydrates, and fats) are broken down into smaller molecules; the conservation and transformation of chemical energy; and the construction of cellular macromolecules from smaller precursors.
- 4. Enzymes are proteins that increase the rate of reaction by lowering the energy of activation • They catalyze nearly all the chemical reactions taking place in the cells of the body • Enzymes have unique three-dimensional shapes that fit the shapes of reactants (substrates)
- 5. What is an enzyme? •An enzyme is a substance that acts as a catalyst in living organisms, regulating the rate at which chemical reactions proceed without itself being altered in the process. • Enzymes are biological catalysts. • A Catalyst is defined as "a substance that increases the rate of a chemical reaction without being itself changed in the process.”
- 6. ENZYMES ⚫DEFINITION ⚫ Enzymes are proteins that functionas biological catalysts. A catalyst is a substance thatspeeds upa chemical reaction but isn’tchanged by the reaction. ⚫Enzymescatalyzeall aspectsof cell metabolism.
- 7. ⚫Enzymes are highly specific to the reactions they catalyze ⚫They alter or speed up the rates of chemical reactions thatoccur in a cell. ⚫They remain unchanged after a chemical reaction. ⚫Theyareaffected by temperature. ⚫Theyareaffected by pH. ⚫Theycatalyze reversible reactions. PROPERTIESOF ENZYMES
- 9. • Catalytic efficiency – high efficiency, 103 to 1017 faster than the correspondingun-catalyzedreactions • Specificity - high specificity , interacting with one or a few specific substratesandcatalyzingonlyonetypeof chemical reaction. • Mild reaction conditions- 37℃, physiological pH, ambient atmosphericpressure
- 11. Chemical composition of enzymes (1) Simple protein (2) Conjugated protein Holoenzyme= Apoenzyme+ Cofactor Coenzyme : loosely bound to enzyme (non- covalently bound). Prosthetic group : very tightly or even covalently bound to enzyme (covalently bound) Cofactor
- 13. Classificationof enzymes Based on their their composition 1) Monomeric enzyme: Monomeric enzymes are enzymes consisting of a single polypeptide chain or subunit. The proteins in the monomeric units are made of polymers of aminoacids.
- 14. 2. Oligomeric enzyme: Oligomeric enzymes consist of two or morepolypeptide chains which are usually linked toeach other by non covalent interactions andnever by peptide bonds. The componentpolypeptide chains are termed sub- units andmay be identical ,they are some times calledprotomers.
- 15. 3.Multienzymecomplex: A multienzyme complex contains several copies of one or several enzymes (polypeptide chains) packed into one assembly. Multienzyme complex carries out a single or a series of biochemical reactions taking place in the cells. It allows to segregate certain biochemical pathways into one pace in the cell.
- 16. Nomenclature • Recommended name •Enzymes are usuallynamed according to the reaction they carry out. •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). •Systematic name (International classification) •By the reactions they catalyze (Six classes)
- 18. DISTRIBUTION ⚫Enzymes are not randomly distributed but are specifically located inside the cells for example ⚫Digestive Enzymes: (Pancreas and stomach) ⚫Glycosol :( oxidation of glucose) ⚫Mitochondria TCA cycle
- 19. How enzymes work 1) Enzymes lower a reaction’s activation energy –All chemical reactions have an energy barrier, called the activation energy, separating the reactants and the products. –activation energy: amount of energy needed to disrupt stable molecule so that reaction can take place.
- 21. What is the difference between an enzyme and a protein? Protein •All enzymes are proteins except some RNAs • not all proteins are enzymes RNA Enzymes
- 22. The activesiteof theenzyme • Enzymes bind substrates to their active site and stabilize the transition state of the reaction. • The active site of the enzyme is the place where the substrate binds and at which catalysis occurs. • The active site binds the substrate, forming an enzyme-substrate(ES) complex. Binding site Active site Catalytic site
- 23. Enzymatic reaction steps 1. Substrate approaches active site 2. Enzyme-substrate complex forms 3. Substrate transformed into products 4. Products released 5. Enzyme recycled
- 24. Enzymesin clinical diagnosis • An enzyme test is a blood test or urine test that measures levels of certain enzymes to assess how well the body’s systems are functioning and whether there has been any tissue damage.
- 25. Common enzymes used for clinical diagnosis alanine aminotransferase(ALT,also called glutamate pyruvate transaminase,GPT) alkaline phosphatase amylase aspartate aminotransferase creatine kinase lactate dehydrogenase
- 26. GROUPS OF ENZYMES THERE ARE SIX MAJOR GROUPS OF ENZYMES
- 27. ENZYME PORTIONS Enzymesarecomposed of: 1.APO ENZYME : Protein portion consisting of aminoacid chains 2. CO- FACTORS activate enzymesand are not protein parts. ⚫HOLOENZYME (conjugated enzyme) ⚫Both cofactors and apoenzymes help to form a conjugated enzyme called holoenzyme.
- 28. 3. SUBSTRATE AND ACTIVE SITE : ⚫Enzymesoperate by binding to a substrate ⚫Thecatalytic (active) site is the portion of the enzyme where substrate binding occurs.
- 29. MECHANISMOF ENZYMEACTION ⚫Proposed by Emil Fischer (1894): the shape of the substrate and the active site of the enzyme are thought to fit together like a key into its lock. ⚫It was suggested by Arrhenius that the shape of the Active Sites of Enzymes is exactly Complementary to the shape of the Substrate. 1. THE LOCK-AND-KEY HYPOTHESIS
- 31. 2. Induced fit hypothesis proposed in 1958 by Daniel E. Koshland, Jr.: the binding of substrate induces a conformational change in the active site of the enzyme. In addition, the enzyme may distort the substrate, forcing it into a conformation similar to that of the transition state A more recent model suggested by Daniel Koshland the Induced- Fit Model. It states that the shape of Active Sites are not exactly Complementary, but are changed according to the substrate molecules
- 33. For example, the binding of glucose to hexokinase induces a conformational change in the structure of the enzyme such that the active site assumes a shape that is complementary to the substrate (glucose) only after it has bound to the enzyme.
- 34. Factors affecting enzyme activity • Concentration of substrate • Concentration of enzyme • Temperature • pH • Activators • Inhibitors
- 35. FACTORS AFFECTING THE RATE OF ENZYME ACTIONS ⚫1. TEMPERATURE ⚫Enzymes havean optimum temperatureatwhich theywork fastest. ⚫Up totheoptimum temperature the rate increases ⚫Abovetheoptimum temperature the ratedecreases
- 36. ⚫2. pH ⚫Enzymes havean optimum pH atwhich theywork fastest. ⚫For mostenzymes this is about pH 7-8 ⚫but a few enzymes can work at extreme pH, such as proteaseenzymes in animal stomachs, which havean optimumof pH 1.
- 37. 3. ENZYME CONCENTRATION ⚫As theenzymeconcentration increases the rateof the reaction increases linearly ⚫Atvery high enzymeconcentration the substrate concentration may become rate-limiting
- 38. 4. SUBSTRATE CONCENTRATION ⚫As the substrate concentration increases, the rate increases because more substrate molecules can collidewith enzyme molecules, so more reactionswill take place
- 39. INHIBITION CAN BE EITHER COMPETITIVE OR NONCOMPETITIVE 1. COMPETITIVE INHIBITION: Competitive inhibition is the interruptionof an enzyme'sability to bind toa substratedue toa different molecule binding to theactivesite.
- 40. 2. NON COMPETITIVE INHIBITION : ⚫Non competitive inhibitors are not similar to the substrateand theydo not bind to theactivesiteof the enzyme. ⚫Theychange theconformation of theactivesite.
- 41. ROLE OF ENZYMES IN THE BODY 1. DEGRADATION REACTIONS (CATABOLIC) 2. SYNTHESIS (ANABOLIC) 3. DIGESTION Enzymesare used fora wide varietyof purposes, such as in digestion. 4.PROTECTION Enzymesarealso used in protection against Pathogens. They can be used to destroy invading Microorganisms.