TheMcGraw-HillCompaniesChapter 8AnIntroductiontoMicrobialMetabolismFoundationsinMicrobiologyEIGHTHEDTTIOKathleenParkTalaroBarryChessCopyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display
Chapter 8 An Introduction to Microbial Metabolism Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display
FEXTheMetabolismofMicrobesCopyright The McGrawHill Comparies, Inc. Permission required for reproduction or displayMetabolism - all chemical andSynthesis of Cell Structuresphysical workings of a cellMacromoleculesSourcesofenergyCarbohydratesCarbohydratesProteinsLipidsLipidsProteinsTwo types of chemical reactions:Catabolism- degradative;CatabolismAnabolismReleases energyATPRequires energyNADHbreaks the bonds of largeraemolecules forming smallerSimple buildingEndproductswithblocksmolecules; releases energyreduced energySugarsCO2, H:OAmino acidsAnabolism-biosynthesis;process that forms largermacromoleculesfromsmallermolecules;requiresenergy input2
2 The Metabolism of Microbes Metabolism – all chemical and physical workings of a cell Two types of chemical reactions: Catabolism – degradative; breaks the bonds of larger molecules forming smaller molecules; releases energy Anabolism – biosynthesis; process that forms larger macromolecules from smaller molecules; requires energy input Synthesis of Cell Structures Sources of energy Carbohydrates Lipids Proteins End products w ith reduced energy CO2, H2O Macromolecules Carbohydrates Proteins Lipids Simple building blocks Sugars Amino acids Catabolism Releases energy Anabolism ATP Requires energy NADH Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Increasing complexity
FEXEnzymesEnzymes are biological catalysts that increase the rate of achemical reaction by lowering the energy of activation (theresistance to a reaction)The enzyme is not permanently altered in the reactionEnzyme promotes a reaction by serving as a physical sitefor specific substrate molecules to positionCopyright The McGraw-HllCompanies, hc. Permission required for reproduction or displayEnergyofactivationintheabsenceofenzymeReactantEnergyof activationinthe福presenceofenzymeInitialstateProductsA?3Final stateProgress ofReaction
3 Enzymes • Enzymes are biological catalysts that increase the rate of a chemical reaction by lowering the energy of activation (the resistance to a reaction) • The enzyme is not permanently altered in the reaction • Enzyme promotes a reaction by serving as a physical site for specific substrate molecules to position Progress of Reaction Energy of activation in the absence of enzyme Energy of activation in the presence of enzyme Products Final state Reactant Initial state Energy State of Reaction Copyright © The McGraw -Hill Companies, Inc. Permission required for reproduction or display
EnzymeStructure Simple enzymes - consist of protein aloneConjugated enzymes or holoenzymescontain protein and nonprotein molecules-Apoenzyme -protein portion- Cofactors - nonprotein portion.Metalliccofactors:iron, copper,magnesium. Coenzymes, organic molecules: vitaminsCopyright The McGraw-HillCompanies, Inc. Permission required for reproduction or displayCoenzymeCoenzymeMetalliccofactorMetallic4cofactorApoenzymes
4 Enzyme Structure • Simple enzymes – consist of protein alone • Conjugated enzymes or holoenzymes – contain protein and nonprotein molecules – Apoenzyme – protein portion – Cofactors – nonprotein portion • Metallic cofactors: iron, copper, magnesium • Coenzymes, organic molecules: vitamins Coenzyme Apoenzymes Coenzyme Metallic cofactor Metallic cofactor Copyright © The McGraw -Hill Companies, Inc. Permission required for reproduction or display
EnzymeExamplesandtheirCofactorsCopyrightTheMcGraw-Hill Companies, Inc.Permission required forreproductionordisplay.TABLE8.2SelectedEnzymes,CatalyticActions,and CofactorsMetallicCofactorEnzymeActionRequiredCatalaseIron (Fe)Breaksdownhydrogen peroxideOxidaseAdds electrons toIron, copper (Cu)oxygenHexokinaseTransfers phosphateMagnesium (Mg)to glucoseUreaseNickel (Ni)Splits urea into anammoniumionNitrate reductaseReduces nitrateMolybdenum (Mo)tonitriteDNA polymeraseSynthesis of DNAZinc (Zn) and Mg5complex
5 Enzyme Examples and their Cofactors
MCHowEnzymes WorkirawHH自品0PlayPauseAudioTextEnzymesare proteins that speed up chemical reactions in the cellCopyrightTheMcGraw-Hill Companies,Inc
FEXApoenzymes:SpecificityandtheActive SiteExhibits primary, secondary, tertiary, and some,quaternary structureSite for substrate binding is active site, or catalytic siteCopyright The McGraw-Hll Companies, Inc. Permission required for reproduction or display.Levels of StructurePrimarySecondaryTertiaryWAs the poly peptide(a)forms intrachain bondsandfolds,itassumesathree-dimensional0(tertiary)state thatdisplays an active siteaS(b) Because eachdiff erent poly peptidefolds differently,each-#-apoenzymewill haveadifferently shaped activesiteQuatemaryAS(c) More complexenzymeshaveaquatenarystructureconsisting ofmore than一one poly peptide. Theactivesimay beformed bythejunction oftwo poly peptides.AS
7 Apoenzymes: Specificity and the Active Site • Exhibits primary, secondary, tertiary, and some, quaternary structure • Site for substrate binding is active site, or catalytic site AS AS Levels of Structure AS AS Primary Secondary Tertiary Quaternary (a) As the poly peptide f orms intrachain bonds and f olds, it assumes a three-dimensional (tertiary ) state that display s an activ e site (AS). (b) Because each dif f erent poly peptide f olds dif f erently, each apoenzy me will hav e a dif f erently shaped activ e site. (c) More complex enzy mes hav e a quaternary structure consisting of more than one poly peptide. The activ e sites may be f ormed by the junction of two poly peptides. Copyright © The McGraw -Hill Companies, Inc. Permission required for reproduction or display
FEXApoenzymes:SpecificityandtheActiveSiteAtemporaryenzyme-substrate unionoccurswhensubstratemoves into active site -induced fitAppropriate reaction occurs; product is formed and releasedCopyright The McGraw -HillCompanies, Inc. Permission required for reproduction or displaySubstrate (S)Products?EScomplexEnzyme(E)Doesnotfit(b)(a)(c)8(d)
8 Apoenzymes: Specificity and the Active Site • A temporary enzyme-substrate union occurs when substrate moves into active site – induced fit • Appropriate reaction occurs; product is formed and released (a) (b) (c) (d) Substrate (S) Products S Does not fit E E E Enzyme (E) ES complex E Copyright © The McGraw -Hill Companies, Inc. Permission required for reproduction or display
Cofactors:SupportingtheWorkofEnzymesCopyright The McGraw -HillCompanies, Inc. Permis sion required for reproduction or display.Chemicalgroup(Ch)Substrate2(S2)Substrate1(S)1.AnenzymeMicronutrientswithacoenzymepositionedtoreactwith twosubstrates.are needed asCoenzymeEnzyme(C)complex(E)cofactors2.Coenzymepicksupachemicalgroupfromsubstrate1Cofactors actas carriers to3.Coenzymeassist thereadiesthechemicalgroupfortransfertoenzyme in itssubstrate2.hactivity4.Final actionisforgrouptobeboundtosubstrate2;alteredsubstrates9arereleasedfromenzyme
9 Cofactors: Supporting the Work of Enzymes • Micronutrients are needed as cofactors • Cofactors act as carriers to assist the enzyme in its activity 1. An enzyme with a coenzyme positioned to react with two substrates. 2. Coenzyme picks up a chemical group from substrate 1. 4. Final action is for group to be bound to substrate 2; altered substrates are released from enzyme. 3. Coenzyme readies the chemical group for transfer to substrate 2. Substrate 2 (S2 ) Coenzyme (C) Chemical group (Ch) Substrate 1 (S1) Enzyme complex (E) S2 S1 C E Ch C E S1 S1 C E Ch Ch Copyright © The McGraw -Hill Companies, Inc. Permission required for reproduction or display. S2 S1
Location of Enzyme ActionExoenzymes -transported extracellularly,where theybreak down large food molecules or harmful chemicals-Cellulase,amylase,penicillinaseEndoenzymes - retained intracellularly and function there- Most enzymes are endoenzymesCopyright The McGraw-Hil Companies, nc. Permission required for reproduction or displaySubstrateProductsActiveProductsenzymeEnzymeInactiveSSubstrateenzymes10EndoenzymesExoenzymes(a)(b)
10 Location of Enzyme Action • Exoenzymes – transported extracellularly, where they break down large food molecules or harmful chemicals – Cellulase, amylase, penicillinase • Endoenzymes – retained intracellularly and function there – Most enzymes are endoenzymes (a) (b) Exoenzymes Endoenzymes Active enzyme Substrate Products Enzyme Substrate Products Inactive enzymes Copyright © The McGraw -Hill Companies, Inc. Permission required for reproduction or display