Enzyme and Vitamins (PDF)

Section 21.1 General Characteristics of Enzymes Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 1  Chapter 21 Chapter Outline 21.1 General characteristics of enzymes...

Section 21.1 General Characteristics of Enzymes Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 1  Chapter 21 Chapter Outline 21.1 General characteristics of enzymes 21.2 Enzyme structure 21.3 Nomenclature and classification of enzymes 21.4 Models of enzyme action 21.5 Enzyme specificity 21.6 Factors that affect enzyme activity 21.7.Extremozymes 21.8 Enzyme inhibition 21.9 Regulation of enzyme activity Copyright ©2016 Cengage Learning. All Rights Reserved. 2  Chapter 21 Chapter Outline 21.10 Prescription drugs that inhibit enzyme activity 21.11 Medical uses of enzymes 21.12 General characteristics of vitamins 21.13 Water-soluble vitamins: Vitamin C 21.14 Water-soluble vitamins: The B vitamins 21.15 Fat-soluble vitamins Copyright ©2016 Cengage Learning. All Rights Reserved. 3  Section 21.1 General Characteristics of Enzymes Enzymes: Proteins that act as catalysts for biochemical reactions – The human body has thousands of enzymes Not consumed during the reaction Most effective catalysts known Most enzymes are globular proteins – A few enzymes are now known that are made of ribonucleic acids (RNA) Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 4  Section 21.1 General Characteristics of Enzymes Undergo all the reactions of proteins including denaturation Enzyme activity is affected by alterations in: – pH – Temperature Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 5  Section 21.1 General Characteristics of Enzymes What are enzymes? a.Cofactors that carry functional groups during biological synthesis b.Specialized catalysts of biochemical reactions c.Structural components of cell membranes d.Both (a) and (b) Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 6  Section 21.1 General Characteristics of Enzymes What are enzymes? a.Cofactors that carry functional groups during biological synthesis b.Specialized catalysts of biochemical reactions c.Structural components of cell membranes d.Both (a) and (b) Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 7  Section 21.2 Enzyme Structure Simple and Conjugated Enzymes Simple enzyme: Enzyme composed only of protein (amino acid chains) Conjugated enzyme: Enzyme that has non- protein and protein parts – Apoenzyme: Protein part of a conjugated enzyme – Cofactor: Non-protein part of a conjugated enzyme – Holoenzyme: Biochemically active conjugated enzyme Apoenzyme + cofactor = holoenzyme Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 8  Section 21.2 Enzyme Structure Cofactors Provide additional chemically reactive functional groups Categories – Simple metal ions - Include Zn2+, Mg2+, Fe (Fe2+, Fe3+), and Cu (Cu+, Cu2+) Supplied to the human body through dietary mineral intake – Small organic molecules - Known as coenzymes Coenzymes: Serve as a cofactor in a conjugated enzyme – Synthesized in the human body using building blocks obtained from other nutrients Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 9  Section 21.2 Enzyme Structure What is the difference between a simple enzyme and a conjugated enzyme? a.Simple enzymes catalyze only one biochemical reaction while conjugated enzymes catalyze a series of biochemical reactions. b.Simple enzymes are composed of only amino acids that are soluble in aqueous media while conjugated enzymes are insoluble enzymes found in cell membranes. c.Simple enzymes are composed only of protein chains while conjugated enzymes have a nonprotein part in addition to a protein part. d.Simple enzymes catalyze simple one step biochemical reactions while conjugated enzymes catalyze two or more complicated biochemical reactions. Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 10  Section 21.2 Enzyme Structure What is the difference between a simple enzyme and a conjugated enzyme? a.Simple enzymes catalyze only one biochemical reaction while conjugated enzymes catalyze a series of biochemical reactions. b.Simple enzymes are composed of only amino acids that are soluble in aqueous media while conjugated enzymes are insoluble enzymes found in cell membranes. c.Simple enzymes are composed only of protein chains while conjugated enzymes have a nonprotein part in addition to a protein part. d.Simple enzymes catalyze simple one step biochemical reactions while conjugated enzymes catalyze two or more complicated biochemical reactions. Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 11  Section 21.3 Nomenclature and Classification of Enzymes Enzymes are named with reference to their function – Focal points - Type of reaction catalyzed and substrate identity Substrate: Reactant in an enzyme-catalyzed reaction – Substance upon which the enzyme acts – Example: In the fermentation process, sugar is converted to alcohol In this reaction, sugar is the substrate Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 12  Section 21.3 Nomenclature and Classification of Enzymes Important Aspects of the Naming Process 1. Suffix -ase identifies a substance as an enzyme – Example: Urease, sucrase, and lipase are all enzyme designations – Exception: Suffix -in is still found in the names of some digestive enzymes Example: Trypsin, chymotrypsin, and pepsin 2. Type of reaction catalyzed by an enzyme is often used as a prefix – Oxidase enzyme catalyzes an oxidation reaction – Hydrolase enzyme catalyzes a hydrolysis reaction Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 13  Section 21.3 Nomenclature and Classification of Enzymes Important Aspects of the Naming Process 3. Identity of substrate is often used in addition to the type of reaction – Examples: Glucose oxidase, pyruvate carboxylase, and succinate dehydrogenase Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 14  Section 21.3 Nomenclature and Classification of Enzymes Practice Exercise Predict the function of the following enzymes. a. Maltase b. Lactate dehydrogenase c. Fructose oxidase d. Maleate isomerase Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 15  Section 21.3 Nomenclature and Classification of Enzymes Practice Exercise Predict the function of the following enzymes. a. Maltase b. Lactate dehydrogenase c. Fructose oxidase d. Maleate isomerase Answers: a. Hydrolysis of maltose b. Removal of hydrogen from lactate ion c. Oxidation of fructose Return to TOC d. Rearrangement (isomerization) of maleate ion Copyright ©2016 Cengage Learning. All Rights Reserved. 16  Section 21.3 Nomenclature and Classification of Enzymes Classes of Enzymes Enzymes are grouped into classes based on the types of reactions they catalyze Class Reaction Catalyzed 1. Oxidoreductases Oxidation–reduction reactions 2. Transferases Functional group transfer reactions 3. Hydrolases Hydrolysis reactions Reactions involving addition or removal of groups 4. Lyases to form double bonds 5. Isomerase Isomerization reactions 6. Ligases Reactions involving bond formation with the participation of ATP Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 17  Section 21.3 Nomenclature and Classification of Enzymes Oxidoreductase Catalyzes an oxidation–reduction reaction – Oxidation and reduction reactions are linked to one another An oxidoreductase requires a coenzyme that is oxidized or reduced, as the substrate is reduced or oxidized Example: Lactate dehydrogenase is an oxidoreductase, and NAD+ is the coenzyme in the reaction Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 18  Section 21.3 Nomenclature and Classification of Enzymes Transferase Catalyzes the transfer of a functional group from one molecule to another Subtypes – Transaminase - Catalyzes the transfer of an amino group from one molecule to another – Kinase - Catalyzes the transfer of a phosphate group from adenosine triphosphate (ATP) to give adenosine diphosphate (ADP) and a phosphorylated product Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 19  Section 21.3 Nomenclature and Classification of Enzymes Hydrolase Catalyzes a hydrolysis reaction – Reaction involves the addition of a water molecule to a bond, which causes the bond to break Hydrolysis reaction is central to the process of digestion – Carbohydrase hydrolyzes glycosidic bonds in oligo- and polysaccharides – Protease effects the breaking of peptide linkages in proteins – Lipase effects the breaking of ester linkages in triacylglycerols Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 20  Section 21.3 Nomenclature and Classification of Enzymes Lyase Catalyzes the addition or the removal of a group to form a double bond in a manner that does not involve hydrolysis or oxidation – Dehydratase - Effects the removal of the components of water from a double bond – Hydratase - Effects the addition of the components of water to a double bond Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 21  Section 21.3 Nomenclature and Classification of Enzymes Isomerase and Ligase Isomerase: Catalyzes the isomerization (rearrangement of atoms) of a substrate in a reaction – Converts it into a molecule, isomeric with itself Ligase: Catalyzes the formation of a bond between two molecules with the participation of ATP – ATP involvement is required as such reactions are energetically unfavorable Requires simultaneous input of energy obtained by the hydrolysis of ATP to ADP Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 22  Section 21.3 Nomenclature and Classification of Enzymes Practice Exercise Which main enzyme class do the enzymes that catalyze the following chemical reactions belong to? Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 23  Section 21.3 Nomenclature and Classification of Enzymes Practice Exercise Which main enzyme class do the enzymes that catalyze the following chemical reactions belong to? Answers: a. Transferase b. Lyase Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 24  Section 21.3 Nomenclature and Classification of Enzymes What function does the substrate perform in an enzyme-catalyzed reaction? a.It is the substance upon which the enzyme acts. b.It is the product of the reaction. c.It acts as a cofactor to carry functional groups. d.It acts as a coenzyme in the reaction. Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 25  Section 21.3 Nomenclature and Classification of Enzymes What function does the substrate perform in an enzyme-catalyzed reaction? a.It is the substance upon which the enzyme acts. b.It is the product of the reaction. c.It acts as a cofactor to carry functional groups. d.It acts as a coenzyme in the reaction. Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 26  Section 21.4 Models of Enzyme Action Enzyme Active Site Active site: Small part of an enzyme’s structure that is involved in catalysis – Formed due to folding and bending of the protein – Usually a crevicelike location in the enzyme Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 27  Section 21.4 Models of Enzyme Action Enzyme–Substrate Complex Intermediate reaction species formed when substrate binds to the active site of an enzyme Reaction conditions within the enzyme–substrate complex are more favorable for the substrate – Results in the faster formation of the product Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 28  Section 21.4 Models of Enzyme Action Lock-and-Key Model and Induced-Fit Model Lock-and-key model – Enzyme has a fixed, rigid geometrical conformation Only substrates with a complementary geometry can be accommodated at the site Induced-fit model – The active site allows for small changes in space to accommodate the substrate Example: How a hand fits into a glove Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 29  Section 21.4 Models of Enzyme Action Forces That Assist Substrate Binding Electrostatic interactions Hydrogen bonds Hydrophobic interactions Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 30  Section 21.4 Models of Enzyme Action What is the area of an enzyme where catalysis of a substrate occurs called? a.Substrate area b.Active area c.Substrate site d.Active site Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 31  Section 21.4 Models of Enzyme Action What is the area of an enzyme where catalysis of a substrate occurs called? a.Substrate area b.Active area c.Substrate site d.Active site Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 32  Section 21.5 Enzyme Specificity Absolute specificity - Enzyme will catalyze only one reaction – Most restrictive of all specificities and is not common – Example: Catalase is an enzyme with absolute specificity for hydrogen peroxide (H2O2) Group specificity - Enzyme will act only on molecules that have a specific functional group – Example: Carboxypeptidase cleaves amino acids, one at a time, from the carboxyl end of the peptide chain Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 33  Section 21.5 Enzyme Specificity Linkage specificity – Enzyme will act on a particular type of chemical bond, rest of the molecular structure is not considered – Most general of the common specificities – Example: Phosphatases hydrolyze phosphate–ester bonds in all types of phosphate esters Stereochemical specificity – Enzyme will act on a particular stereoisomer – Chirality is inherent in an active site ʟ-amino-acid oxidase will only catalyze the oxidation of the ʟ-form of an amino acid but not its ᴅ-form Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 34  Section 21.5 Enzyme Specificity Which of the following statements is true about an enzyme’s absolute specificity? a.Enzyme will catalyze a particular reaction for only one substrate. b.Enzyme will catalyze the same reaction for several substrates. c.Enzyme can distinguish between stereoisomers of one substrate. d.Enzyme recognizes the same type of linkage in different substrates. Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 35  Section 21.5 Enzyme Specificity Which of the following statements is true about an enzyme’s absolute specificity? a.Enzyme will catalyze a particular reaction for only one substrate. b.Enzyme will catalyze the same reaction for several substrates. c.Enzyme can distinguish between stereoisomers of one substrate. d.Enzyme recognizes the same type of linkage in different substrates. Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 36  Section 21.6 Factors That Affect Enzyme Activity Enzyme Activity Measure of the rate at which an enzyme converts substrate to products in a biochemical reaction Factors that affect enzyme activity – Temperature – pH – Substrate concentration – Enzyme concentration Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 37  Section 21.6 Factors That Affect Enzyme Activity Temperature Higher temperature results in higher kinetic energy – Causes molecules to move faster and collide frequently – Increases the rate of reaction Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 38  Section 21.6 Factors That Affect Enzyme Activity Temperature Optimum temperature – Temperature at which an enzyme exhibits maximum activity – Optimum temperature for human enzymes is 37°C (body temperature) Increase in temperature (high fever) initiates enzyme denaturation Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 39  Section 21.6 Factors That Affect Enzyme Activity pH Small changes in pH can result in denaturation of proteins Optimum pH: pH at which an enzyme exhibits maximum activity – Optimum pH range for most enzymes - 7.0 to 7.5 – Exceptions Pepsin: Optimum pH = 2.0 Trypsin: Optimum pH = 8.0 Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 40  Section 21.6 Factors That Affect Enzyme Activity Substrate Concentration At a constant enzyme concentration, the enzyme activity increases with increased substrate concentration Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 41  Section 21.6 Factors That Affect Enzyme Activity Substrate Concentration Limit of substrate saturation – Substrate concentration reaches its maximum rate – All the active sites are full Turnover number: Number of substrate molecules converted to product per minute by one molecule of enzyme under optimum conditions of temperature, pH, and saturation Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 42  Section 21.6 Factors That Affect Enzyme Activity Enzyme Concentration Enzymes are not consumed in the reactions they catalyze At a constant substrate concentration, enzyme activity increases with the increase in enzyme concentration – Greater the enzyme concentration, greater the reaction rate Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 43  Section 21.6 Factors That Affect Enzyme Activity Practice Exercise Describe the effect that each of the following changes would have on the rate of a reaction that involves the substrate sucrose and the intestinal enzyme sucrase. a. Decreasing the sucrase concentration b. Increasing the sucrose concentration c. Lowering the temperature to 10ºC d. Raising the pH from 6.0 to 8.0 when the optimum pH is 6.2 Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 44  Section 21.6 Factors That Affect Enzyme Activity Practice Exercise Describe the effect that each of the following changes would have on the rate of a reaction that involves the substrate sucrose and the intestinal enzyme sucrase. a. Decreasing the sucrase concentration b. Increasing the sucrose concentration c. Lowering the temperature to 10ºC d. Raising the pH from 6.0 to 8.0 when the optimum pH is 6.2 Answers: a. Decreases rate b. Increases rate c. Decreases rate d. Decreases rate Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 45  Section 21.6 Factors That Affect Enzyme Activity What factors affect enzyme activity? a.Enzyme and substrate concentration b.Temperature c.pH d.All of the above Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 46  Section 21.6 Factors That Affect Enzyme Activity What factors affect enzyme activity? a.Enzyme and substrate concentration b.Temperature c.pH d.All of the above Return to TOC Copyright ©2016 Cengage Learning. All Rights Reserved. 47  Section 21.7 Extremozymes Extremeophiles Organisms that thrive in extreme environments – Acidophiles - Optimal growth at pH levels of 3.0 or below – Alkaliphiles - Optimal growth at pH levels of 9.0 or above – Halophiles - Live in highly saline conditions (>0.2 M NaCl) – Hyperthermophiles - Thrive at temperatures between 80°C and 122°C – Piezophiles - Grow under high hydrostatic pressure – Cryophiles - Grow at temperatures