【生物化学】Nucleotide-Metab课件

NucleotideMetabolism

NucleotideMetabolism

1CellularRolesofNucleotidesEnergymetabolism(ATP)*Monomericunitsofnucleicacids*RegulationofphysiologicalprocessesAdenosinecontrolscoronarybloodflowcAMPandcGMPserveassignalingmoleculesPrecursorfunction-GTPtotetrahydrobiopterninCoenzymecomponents-5’-AMPinFAD/NAD+Activatedintermediates-UDPGlucoseAllostericeffectors-regulatethemselvesandothersCellularRolesofNucleotidesE2HowIhopetomakethisatleastbearableifnotmildlyinterestingPurinesandPyrimidinesSynthesis(denovoandsalvagepathways)DegradationRelevantdiseasestatesRelevantclinicalapplicationsYouarenotresponsibleforanystructuresHowIhopetomakethisatlea3PurinesandPyrimidinesAdenineGuanineThymine/UracilCytosineTwoPurinesTwoPyrimidinesPurinesandPyrimidinesAdenine4SynthesisPathwaysForbothpurinesandpyrimidinestherearetwomeansofsynthesis(oftenregulateoneanother)denovo(frombitsandparts)salvage(recyclefrompre-existingnucleotides)SalvagePathwaydenovoPathwaySynthesisPathwaysForbothpur5ManyStepsRequireanActivatedRiboseSugar(PRPP)5’ManyStepsRequireanActivate6denovoSynthesisCommittedstep:ThisisthepointofnoreturnOccursearlyinthebiosyntheticpathwayOftenregulatedbyfinalproduct(feedbackinhibition)XdenovoSynthesisCommittedste7PurineBiosynthesis(denovo)Atomsderivedfrom:AsparticacidGlycineGlutamineCO2TetrahydrofolateAlsorequires4ATP’sPurinesaresynthesizedontheRiboseringCommittedStepInhibitedbyAMP,GMP,IMPXPurineBiosynthesis(denovo)A8PurineBiosynthesis(denovo)IMPGMPAMPATPGTP(Abunchofstepsyoudon’tneedtoknow)(InosineMonophosphate)FeedbackInhibitionPurineBiosynthesis(denovo)I9ThepathwayforpurinebiosynthesisThepathwayforpurinebiosyntThesynthesisofAMPandGMPfromIMPThesynthesisofAMPandGMPfThemetabolicoriginofthenineatomsinthepurineringsystemThemetabolicoriginoftheniSalvagePathwayforPurinesHypoxanthineorGuanine+PRPP=IMPorGMP+PPiHypoxanthineguanosylphosphoribosyltransferase(HGPRTase)Adenine+PRPP=AMP+PPiAdeninephosphoribosyltransferase(APRTase)SalvagePathwayforPurinesHyp13Lesch-NyhanSyndromeAbsenceofHGPRTaseX-linked(GeneonX)OccursprimarilyinmalesCharacterizedby:IncreaseduricacidSpasticityNeurologicaldefectsAggressivebehaviorSelf-mutilationLesch-NyhanSyndromeAbsenceof14BiosynthesisofPyrimidinesPyrimidineringsaresynthesizedindependentoftheriboseandtransferredtothePRPP(ribose)GeneratedasUMP(uridine5’-monophosphate)Synthesizedfrom:GlutamineCO2AsparticacidRequiresATPUracilCytosineBiosynthesisofPyrimidinesPyr15RegulationofPyrimidineBiosynthesisRegulationoccursatfirststepinthepathway(committedstep)2ATP+CO2+Glutamine=carbamoylphosphateInhibitedbyUTPIfyouhavelotsofUTParoundthismeansyouwon’tmakemorethatyoudon’tneedFeedbackInhibitionXRegulationofPyrimidineBiosy16ThepyrimidinebiosyntheticpathwayThepyrimidinebiosyntheticpaHereditaryOroticAciduriaDefectindenovosynthesisofpyrimidinesLossoffunctionalUMPsynthetaseGenelocatedonchromosomeIIICharacterizedbyexcretionoforoticacidResultsinsevereanemiaandgrowthretardationExtremelyrare(15casesworldwide)TreatedbyfeedingUMPHereditaryOroticAciduriaDefe18WhydoesUMPCure

OroticAciduria?Disease(-UMP)NoUMP/excessorotateDisease(+UMP)RestoredepletedUMPDownregulatepathwayviafeedbackinhibition(Lessorotate)CarbamoylPhosphateUMPOrotateUMPSynthetaseXUTPFeedbackInhibitionWhydoesUMPCure

OroticAcid19Biosynthesis:PurinevsPyrimidineSynthesizedonPRPPRegulatedbyGTP/ATPGeneratesIMPRequiresEnergySynthesizedthenaddedtoPRPPRegulatedbyUTPGeneratesUMP/CMPRequiresEnergyPurinePyrimidineBothareverycomplicatedmulti-stepprocesswhichyourkindlyprofessordoesnotexpectyoutoknowindetailBiosynthesis:PurinevsPyrimi20PyrimidineSalvageCanalsobesalvagedbyreactionswithPRPP-CatalyzedbyPyrimidinephosphoribosyltransferaseNucleosidekinaseDegradationpathwaysarequitedistinctforpurinesandpyrimidines,butsalvagepathwaysarequitesimilarPyrimidineSalvageCanalsobe21Waitaminute:

Sofarwe’veonlymade

GMP,AMP,andUMPSohowtheheckarewesupposedtomakeDNA?Waitaminute:

Sofarwe’veon22BeyondAMP,GMPandUMPPurineBiosynthesisPyrimidineBiosynthesisAMPGMPUMPButotherformsofthesenucleotidesareneededBeyondAMP,GMPandUMPPurine23TwoProblemsThesearemonophosphates(i.e.GMP)-weneedtriphosphates(i.e.GTP)forbothDNAandRNAsynthesisTheseareribonucleotides-that’sfineforRNAbutwealsoneedtomakeDNASynthesisofribonucleotidesfirstsupportstheRNAworldtheoryTwoProblemsThesearemonophos24SynthesisofUTP/CTP

(EasyProblem)UMPUDPUTPNucleotideDiphosphokinaseATPATPCTPTTPATP+GlutamineSynthesisofUTP/CTP

(EasyPr25CTPsynthesisfromUTPCTPsynthesisfromUTPBeyonddGTP,dATPanddUTPSofarwe’vemadeGTP,ATP,andUTPforincorporationintoRNAAlsodGTPanddATPforincorporationintoDNAWestillneeddCTPforbothRNAandDNAWealsoneedtogeneratedTTPforDNABeyonddGTP,dATPanddUTPSof27SpecificKinasesConvertNMPtoNDPMonophosphatekinasesarespecificforthebasesNucleosideMonophosphatesNucleosideDiphosphatesNMPNDPMonophosphateKinasesAMP+ATP2ADPGMP+ATPGDP+ADPAdenylateKinaseGuanylateKinaseSpecificKinasesConvertNMPt28ConversionofRibonucleotidestoDeoxyribonucleotides1´2´3´4´5´1´2´3´4´5´BASEBASEDeoxyribonucleosideRibonucleosideSomehowweneedtogetridofthisdamnoxygenRibonucleotideReductaseConversionofRibonucleotides29RibonucleotideReductaseCatalyzesconversionofNDPtodNDPHighlyregulatedenzymeRegulatesthelevelofcellulardNTPsActivatedpriortoDNAsynthesisControlledbyfeedbackinhibitionRibonucleotideReductaseCataly30【生物化学】Nucleotide-Metab课件E.coliribonucleotidereductaseE.coliribonucleotidereductas【生物化学】Nucleotide-Metab课件ThefreeradicalmechanismofribonucleotidereductionThefreeradicalmechanismofElectrontransferfromNADPHtoRRElectrontransferfromNADPHtRibonucleotidereductase-enzymeorganizationandregulationactivityspecificityRibonucleotidereductase-enzy36RegulationofribonucleotidereductaseCellCycle[lateG1]AllostericregulationOverallactivity:+ATP,-dATPSubstratespecificity:ATPstimulateCDP,UDPreduction(d)TTPstimulatesGDPreduction(d)TTPinhibitsCDP,UDPreductiondGTPstimulatesADPreduction,inhibitsGDP,CDP,UDPreductionRegulationofribonucleotider37DNAsynthesisSynthesisofdeoxyribo-nucleotides---reductionatthe2’-positionoftheriboseringofnucleosidediphosphatesDNAsynthesisdNDPtodNTP(thefinalstep)OncedNDPsaregeneratedbyribonucleotidereductaseageneralkinasecanphosphorylatetomakethedNTP’sSofarwe’vemade(d)GTP,(d)ATP,and(d)CTPWhataboutTTP?dNDPtodNTP(thefinalstep)O39SynthesisofTTP

(HardProblem)MethylgroupisprovidedbyN5,N10-MethylenetetrahydrofolateDihyrofolatereductaserechargestheDihydrofolatetoN5,N10-MethylenetetrahydrofolatedUMPdTMPThymidylateSynthaseCH3SynthesisofTTP

(HardProblem40RoleofFolateindTMPSynthesisDihydrofolateReductasedUMPdTMPThymidylateSynthaseDihydrofolateN5,N10-MethylenetetrahydrofolateTetrahydrofolateRoleofFolateindTMPSynthes41【生物化学】Nucleotide-Metab课件PurineDegradationSequentialremovalofbitsandpiecesEndproductisuricacidUricacidisprimate-specificXanthineUricAcidOtherspeciesfurthermetabolizeuricacidExcretedinUrineXanthineOxidasePurineDegradationSequentialr43PurinecatabolisminanimalsPurinecatabolisminanimalsExcessUricAcidCausesGoutPrimarygout(hyperuricemia)InbornerrorsofmetabolismthatleadtooverproductionofUricAcidOveractivedenovosynthesispathwayLeadstodepositsofUricAcidinthejointsCausesacutearthriticjointinflammationOffalfoodssuchasliver,kidneys,tripe,sweetbreadsandtongueAvoid:XanthineUricAcidXanthineOxidaseAllopurinolXExcessUricAcidCausesGoutPr45【生物化学】Nucleotide-Metab课件【生物化学】Nucleotide-Metab课件ImmunodeficiencyDiseasesAssociatedwithPurineDegradationDefectinadenosinedeaminaseRemovesaminefromadenosineSCID-severecombinedimmunodeficiency“BubbleBoy”DiseaseDefectinbothB-cellsandT-cells(DiseaseofLymphocytes)Patientsextremelysusceptibletoinfection-hencetheBubbleLymphocyteImmunodeficiencyDiseasesAsso48TherapiesforSCIDCanbediagnosedininfantsthroughasimplebloodtest(whitecellcount)BonemarrowtransplantforinfantsFamilialdonorContinuedadministrationofadenosinedeaminase(ADA-PEG)Genetherapy-repairdefectivegeneinT-cellsorbloodstemcellsTherapiesforSCIDCanbediagn49PyrimidineDegradationPyrimindineringscanbefullydegradedtosolublestructures(Comparetopurinesthatmakeuricacid)Degradationpathwaysarequitedistinctforpurinesandpyrimidines,butsalvagepathwaysarequitesimilarPyrimidineDegradationPyrimind50PyrimidinedegradationPyrimidinedegradationSummary>90%ofpurinesaresalvagedMostdenovosynthesisinliver,highlyregulatedCrossregulationofpurineandpyrimidinenucleotidebiosynthesisassuresbalancedlevelsofthesemetabolitesDisruptionofsalvageorcatabolismleadstodiseaseSummary>90%ofpurinesaresal52AntimetabolitesOftendrugsthatinhibitcellgrowthareusedtocombatcancerManyofthesecompoundsareanaloguesofpurineandpyrimidinebasesornucleotidesManyofthesedrugsmustbeactivatedbycellularenzymesTheyaffectnucleicacidsynthesisandtumorcellstendtobemoresusceptiblesincetheyaredividingmorerapidlyAntimetabolitesOftendrugstha536-Mercaptopurine(6-MP)PurineAnalogueUsedclinicallytocombatchildhoodleukemiaSince1963cureratehasincreasedfrom~4%togreaterthan80%PRPP+6-MP6-mercaptopurineribonucleotideInhibitorofCommittedStepindenovoPurineBiosynthesisThisreactionismoreactiveintumorcells6-Mercaptopurine(6-MP)Purine54CytosineArabinose(araC)Metabolizedtocytosinearabinose5’-triphosphate(araCTP)AnalogueofCTPIncorporatedintoDNAandinhibitschainsynthesisUsedextensivelyforacuteleukemiasCytosineArabinoseDiffersonlyinthesugarCytosineRiboseCytosineArabinose(araC)Metab55【生物化学】Nucleotide-Metab课件AZTasanAnti-HIVAgentAzido-3’-deoxythymidinePyrimidineAnalogueHIVisaretrovirusRNAgenomethatisreverse-transcribed