生物体中所有化学反应之总和

1Chapter5Microbialmetabolism2I.CatabolicandanabolicreactionsMetabolism:生物體中所有化學反應之總和.Catabolism:degradation(放能)Anabolism:synthesis(吸能)能量反應:ATPFig.5.134II.EnzymesEnzymes:biocatalystActivationenergySubstrate,product.ex:sucroseglucose+fructoseTurnovernumber(TON)sucraseEnzyme活性:IU,SA5II-1.Namingenzymes字尾~ase.分六大類(Table5.1)67II-2.EnzymecomponentsApoenzyme+cofactor=holoenzymecofactor可為金屬離子orcoenzyme…Coenzymes:多由vitamins衍生而來.ex:NAD+,NADP+,FMN,FAD,CoA…(Table5.2)Fig.5.28ex:CoQex:FMN,FADex:NAD+,NADP+910II-3.Themechanismofenzymaticaction1.受質接觸enzyme表面之activesite.2.形成enzyme-substratecomplex.3.Substrate因其分子之重新排列,其分子之降解or與其他受質之結合而使受質之架構改變.4.Substrateproduct,由E-Scomplex被釋放出來.5.Enzyme本身未改變,其可加速化學反應.Fig.5.3a&5.3b“Lockandkeymodel”“Induced-Fitmodel”11drug12II-4.FactorsinfluencingenzymaticactivityTemerature:denaturationpHSubstrateconc.InhibitorsFeedbackinhibtion(end-productinhibition)Fig.5.5Fig.5.4Fig.5.6Fig.5.713TemppH[S]雙曲線1415NCICI1617II-5.Ribozymes如enzyme般具催化功能,對RNA具專一性.具較小之受質範圍.18III.EnergyproductionCatabolicreactionATP19III-1.Oxidation-reductionreactionsOxidation:失去e-,reduction:得到e-.DehydrogenationFig.5.8Fig.5.9202122III-2.ThegenerationofATP加入~p:phosphorylationThreetypes:1.Substrate-levelphosphorylation2.Oxidativephosphorylation:ETC3.Photophosphorylation:只發生含葉綠體且行光合作用之cell.Fig.5.1323NADFAD(FMN)CoQCytO2H2O24IV.MetabolicpathwaysofenergyproductionsABCDEFNAD+NADH+H+ADP+PATPO2CO2H2OEnd-productStartingmaterial12345By-productsorwasteproducts25V.CarbohydratecatabolismRespiration&fermentationGlucose之respiration含threesteps:1.Glycolysis2.Krebscycle3.ETCFig.5.102627V-1.GlycolysisTwostages:1.Preparatorystage2.Energy-conservingstageFig.5.112829V-2.AlternativestoglycolsisThepentosephosphatepathway(PPP)1.或稱hexosemonophosphateshunt(HMS)2.形成pentosenucleicacid;glucose;aminoacid.3.產生NADPH.4.利用此pathway之微生物:Bacillussubtilis,E.coli,Leuconostocmesenteroides&Enterococcusfaecalis.30TheEnter-Doudoroffpathway1.G(-):Rhizobium,Pseudomonas&Agrobacterium.G(+)則不行pathway.2.實驗室鑑定Pseudomonas.31V-3.CellularrespirationdefinedRespiratory:物質經氧化作用產生ATP之過程,且其最終之電子接受者為無機物者.Aerobes,anaerobesFig.5.1032V-3-1AerobicrespirationTheKrebscycle=Tricarboxylicacidcycle(TCAcycle)=CitricacidcycleTheelectrontransportchain(ETC)1.Flavoproteins(Fp)2.Cytochromes3.Ubiquinones(coenzymeQ;CoQ)Fig.5.12Fig.5.13“Chemiosomticmechanism”333435V-3-2ThechemiosmoticmechanismofATPgenerationChemiosmosis1.Protonpump2.Concentrationgradient,electricalchargegradient,electrochemicalgradient,potentialenergy…“protonmotiveforce”3.ATPsynthaseFig.5.14Fig.5.15363738V-3-3AsummaryofaerobicrespirationNADH:3ATP,FADH2(FMNH2):2ATP原核cell:38ATP,真核cell:36ATP(Table5.3)Fig.5.16394041V-3-4Anaerobicrespiration最終之電子接受者異於氧氣之無機物質,ex:Pseudomonas&Bacillus---利用NO3-(nitrogencycle),Desulfovibrio---SO4-2H2S(sulfurcycle),細菌---CO3-2CH442V-3-5Fermentation定義:1.由醣類&aminoacid,organicacids,purines,pyrimidines獲得能量之過程.2.不需O2參與.3.不需Krebscycle&ETC參與.4.以有機物質作為最終電子接受者.5.產生少量ATP,主要能量貯存於中間產物如lactateðanol中.Fig.5.1743圖5.17發酵作用。小插圖顯示發酵作用與整體能量產生之關係。(a)發酵作用，第一步驟為糖酵解作用，葡萄糖被分解為丙酮酸。第二步驟中，由糖酵解作用所產生之還原態輔酶及其相關物質(如NADH,NADPH)提供電子及質子給丙酮酸以形成發酵產物。(b)不同發酵作用之終產物。於發酵作用中、ATP只於糖酵解作用中產生。44V-3-5(1)Lacticacidfermentation首要路徑為glycolysis.Glucose2pyruvate2lactateLacticacidbacteria:Streptococcus&Lcatobacillus為[homolacticorhomofermentativebacteria]可導致食品腐敗,但可生產yogurt,sauerkraut&pickles.無氧Fig.5.18Fig.5.114546V-3-5(2)AlcoholfermentationGlucose2pyruvate2aldehyde+2CO2酵母菌(Saccharomyces),為[heterolacticorheterofermentativebacteria]無氧2ethanolFig.5.1847484950VI.LipidcatabolismFat:fattyacids+glycerol微生物可利用lipase將脂肪分解為fattyacids&glycerolTCAcycleFig.5.205152VII.Proteincatabolism微生物利用proteases&peptidases分解蛋白質為aminoacids(A.A.)TCAcycleDeamination:A.A.之--NH2被移除轉化成NH4+Decarboxylation:Dehydrogenation:53VIII.BiochemicaltestsFermentation:media含蛋白質,單一醣類,pH指示劑&Durhamtube.微生物代謝產生之廢棄物,可被另一微生物利用為其碳源及能量來源.如Acetobacter:yeastethanolPropionibacterium:lactatepyruvateTCAcycle代謝過程中產生propionicacid&CO2Swisscheese之孔洞即CO2造成Fig.5.19545556IX.PhotosynthesisPhytosynthesis:將光能化學能所產生之能量將CO2醣類.Phyto-:陽光or光線,synthesis:合成.利用CO2之碳原子合成醣類亦稱carbonfixation.Cyanobacteria,algae&greenplants可行phytosynthesis.Reaction:6CO2+12H2O+lightenergyC6H12O6+6O2+6H2O57Phytosynthesis可分twostages:1.Lightreactionsorlight-dependentreactions:lightenergy將ADP+PiATP,NADPHNADP.2.Darkreactionsorlight-independentreactions:利用ATP之能量及電子將CO2醣類.58IX-1.Thelightreaction:photophosphorylation為ATP產生方式之一,onlyinphytosyntheticcells.利用chlorophyll並激發分子中之電子.Greenplants,algae&cyanobacteria:chlorophylla,位於thylakoids之膜中.Otherbacteria:bacteriochlorophylls被激發之電子如呼吸作用之ETC,再藉chemiosmosis自ADPATP,在cyclicphotophosphorylation,電子再回到chlorophyll中.59Noncyclicphotophosphorylation:電子並未回到chlorophyll中,而是與NADPHbinding.Chlorophyll失去之電子由H2OorH2S獲得.產物為ATP,O2&NADPH.Fig.5.23b6061XI-2.Thedarkreaction:theCalvin-Bensoncycle不需light.包括Calvin-Bensoncyclepathway.將CO2醣類.Fig.5.246263X.AsummaryofenergyproductionmechanismsPhotosyntheticpigmentsAerobicrespiration:O2為最終之電子接受者.anaerobicrespiration:NO3-