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Enzymes Activation and Deactivation

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Enzymes Activation and Deactivation. November 19 th , 2012. Enzymes are Not Consumed in Reaction. https://www.youtube.com/watch?v=0XjyAkeQJag&feature=related. Factors Effecting Enzymes. Enzymes are not perfect They respond to environmental conditions - PowerPoint PPT Presentation

Enzymes Activation and Deactivation

Enzymes Activation and DeactivationNovember 19th, 2012Enzymes are Not Consumed in Reactionhttps://www.youtube.com/watch?v=0XjyAkeQJag&feature=related Factors Effecting EnzymesEnzymes are not perfectThey respond to environmental conditionsThey work depending on various factors which are?________, ___________, _____________Changing these factors effects? _____________

Enzyme under StresspHAn decrease in pH, increases the [H+] ion concentration in solutionAn increase in pH, increases the [OH-] ion concentration in solutionThese ions interfere with hydrogen bonds and ionic bondsChanging the conformation of the enzymes specifically the active siteActivity of enzyme is affected

Optimal pH

Different enzymes have different optimum pHs At optimum pH the active site is the shape most complementary to the shape of their SubstrateAt optimum pH, the rate of reaction is highestLarge changes in pH can cause enzymes to Denature and permanently loose their function

Temperature Effects EnzymesGenerally, enzymes have a narrow range of temperature they work in, Why?At the optimal temperature enzymes are most active

Increase Temperature What increases? energyMakes the substrate more active in solution. So? More chances of substrate colliding with active site. Makes the enzyme more flexible. Puts strain on weaker bonds. Pass a certain point enzymes denature. What does it mean to denature? active site changesDecrease TemperatureMakes the enzyme less flexible, Pass a certain point enzymes do not function properlyNot enough energy present

Taq PolymeraseEnzyme comes from Thermus Aquaticus, a species that thrive in hot springs and heat vents. Functions at high temperature Used in Polymerase Chain Reaction (PCR)Can make multiple copies of a DNA sample using only a small amount.PCR can be used for a forensic investigation, genetic diseases, drug discovery and detection of pathogens

Temperature CurveVarious thermophillic organisms have their own type of DNA polymerase such as Pfu Polymerase (Pyrococcus furiosus) versus Taq Polymerase

Regulation of TemperatureEndotherms can maintain body temperatureHeat is produced and regulated by the body, How?Ectotherms do not maintain a body temperatureLess sensitive to changes in body temperatureEndothermic organisms are mammals, birds and some fish Most enzymes in the human body have an optimal temperature of 37C

ConcentrationWhat is concentration?

Will the concentration of substrate the rate of reaction?

Will the concentration of enzyme effect the rate of reaction?

Substrate ConcentrationAdding more substrate increases rate of the reactionMore substrate molecule collide with active siteAt a certain point adding more substrate has no more effect. Enzyme active site is saturated

Enzyme ConcentrationIf an enzyme is saturated what can you do?Increasing enzyme concentration, increases the rate of reactionWhy does the graph level off?

Enzyme RegulationNovember 20th & 21st, 2012Biochemical Processhttp://www.iubmb-nicholson.org/animaps.html

Enzyme RegulationThere are enzymes for each specific reaction of the human bodyThere is a need to control enzyme activityRegulation is efficiencyEnzymes can be activated and inhibited

Road MapAspirinCyclooxygenase 2 (COX2) makes prostaglandinsThese chemical are involved in inflammationInflammation is felt as pain and swelling in bodyAspirin reacts with the amino acid serine irreversibly, blocking the active site, substrate can not bindOther pain killers such as ibuprofen (Advil) bind less strongly, are reversible bound

InhibitionEnzyme inhibitors are substances that interfere with catalysisInhibitors slow down the rate of reactionInhibitors can be reversible or irreversibleIrreversible inhibition halts enzymatic reaction permanentlyReversible inhibition slows down the reaction temporarily Inhibitors can act in a competitive or non competitive form and interfere with the reaction Competitive InhibitionCompetitive inhibition: Enzyme inhibitors prevent the formation of Enzyme-Substrate complexes because they have a similar shape to the substrate molecule.

Prevents enzyme from carrying out reaction it is suited for

Enzyme with Active Site Specific for SubstrateSubstrateInhibitorInhibitor Competes with Substrate for the Active SiteCompetitive InhibitionInhibitor has a different shape than the substrate but complements the active siteInhibitor does not react since it has different structure than the substrate. Reaction rate is decreased since fewer substrate molecules can bind to the enzymeInhibition is typically temporary, the inhibitor eventually leaves the active siteInhibition depends on the relative concentrations of substrate and inhibitor, both compete for place in enzyme active site

Methanol Poisoning Methanol if ingested is oxidized to formaldehyde and formic acidAttack on the optic nerve causes blindness. Methanol found in engine fuel,solvents, window cleaner, andantifreeze

Source: http://curriculum.toxicology.wikispaces.net/

Ethanol Competes with MethanolEthanol competitively inhibits the oxidation of methanol by Alcohol Dehydrogenase Ethanol is oxidized in preference to methanolOxidation of methanol is slowed down Toxic by-products do not have chance to accumulate.

Source: http://curriculum.toxicology.wikispaces.net/ Pennicillin, an antibiotic, works against disease causing bacteria Stops cell wall cross-linking permanentlyInactivates transpeptidase, used to build cross-linked peptidoglycan layer in the membraneThe cross-linking peptide chains have repeats of D-AlaninePennicillin also has a repeat of D-Alanine-D-Alanine

E.Coli cells can not grow and dieSuccinate Dehydrogenase InhibitorSuccinate Dehydrogenase catalyzes the conversion of succinate to fumerate, an important biochemical reaction in cellular respiration. Malonate inhibits this reaction competitivelyUsed to find active sitechemistryUsed to study inborn errors of metabolism

Non-Competitive InhibitionNon-competitive inhibition: enzyme inhibitors prevent the formation of Enzyme-Product Complexes. Inhibitors prevent the substrate to react and form into productNon-competitive inhibitors bind to a site other than the Active SiteBinding causes conformational changes that change the tertiary structure of the enzymeThus, enzyme can not catalyze reaction

Non-Competitive Inhibition

SubstrateNon-competitive InhibitorEnzyme Active Site Complementary to SubstrateNon-Competitive ReactionSince they do not compete with substrate molecules, non-competitive inhibitors are not affected by substrate concentration.Many non-competitive inhibitors are irreversible and permanent, and effectively denature the enzymes which they inhibit. However, there are a lot of non-permanent and reversible non-competitive inhibitors that are vital in controlling metabolic functions in organisms.

Cyanide PoisoningAnother enzyme found in cellular respiration is cytochrome oxidase, one of the most important enzymes in the electron transport chain of reactions that occurs in the mitochondria inner membraneHere oxygen is reduced and 34 ATP molecules are made.

Cyanide Poisoning Cyanide acts as a non-competitive inhibitor for cytochrome oxidase complexCyanide does not compete for the active sites of the enzyme because it has no similarity to the substrate cytochrome Cyanide attaches to another site on the enzyme and disrupts the enzyme's shape. This brings the electron transport chain to a haltNo energy can be derived out of respiration Hydrogen cyanide inhibits metal-containing enzymes in the body, such as cytochrome c-oxidase, which contains iron

Irons in Enzymes Chemical catalyst are usually metals Many enzymes get their ability to catalyze reactions due to metals found in the active siteOne common metal used is iron Fe2+ that is found in a protoporphyrin ring

FerrochelataseFerrochetalase inserts iron into protoporphyrin rings Lead forms covalent bonds with the sulphydryl side chains of the amino acid cysteine in the enzyme and prevents catalytic activityThe binding of the heavy metal shows non-competitive inhibition because the substrate still has access.

Chymotrypsin Chymotrypsin is an enzyme which hydrolyzes peptides bondsIn its active site there are three amino acids Histidine57, Serine195 and Asparagine102 known.

Hydrogen Ion Inhibits ChymotrypsinThese amino acids allow for the substrate to be cleaved. By lowering pH, amino acids in the active site no longer accept hydrogen proton since Asp102 becomes protonated (hydrogens added) Hydrogen ion acts as a non-competitive inhibitor by preventing catalysis but do not prevent the substrate from binding to the active site.

Biochemical PathwayA biochemical pathway is a series of step reactions leading to a productEnzymes lie in biochemical pathways There are specific enzymes for each reaction stepMetabolism is a sum of biochemical pathways and is made of anabolic and catabolic processes

Need to Regulate There are so many pathways that are incorporated in the metabolic system of the human bodyAn efficient process is needed to regulate the use of resources and ensure that only what is required is being produced or broken downEnzymes can be regulated by the ability to be activated and deactivated when needed

Allosteric Enzyme RegulationAn allosteric site, a site away from the active site,can bind molecules to change conformation of the enzyme.At the allosteric site for an inhibitor, binding of an inhibitor causes a conformational change such that the active sites of an enzyme are non complementary to the substrate.An activator can bind to its allosteric site to open or improve the fit between substrate and enzyme. Feedback InhibitionIn a biochemical pathway, by controlling an earlier step, the next series of reaction steps can be controlledUsually the end product in a chain of reactions is an inhibitor of an earlier enzyme in the chain to stop the creation of more productProcess is self-regulating and cell resources are not wasted by making more product than needed

Feedback Inhibition Using an Allosteric SiteRegulation of GlycolysisGlycolysis is biochemical process where glucose is broken down to pyruvatePyruvate is used in mitochondria in the process of aerobic respiration to derive ATP Pyruvate kinase is the enzyme that converts phosphenolpyruvate to pyruvate in glycolysisThis enzyme is the third regulated enzyme of glycolysis ATP and alanine act as allosteric inhibitors of pyruvate kinase

Feedback Inhibition of Pyruvate

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