Protein-Degradation-and-教學(xué)講解課件

ProteinDegradation&AAMetabolismProteinDegradation&AAMetab1ProteindegradationExtracellulardegradationIntracellulardegradation

ATP-independentoccursinlysosomes

ATP-dependent

i)N-endruleand“PEST”sequenceii)TheroleofUbiquitin(泛素）

iii)Proteasome（蛋白酶體）

iiii)HighlyregulatedProteindegradation2N-endruleAprotein's

half-life

correlateswithits

N-terminalresidue.ProteinswithN-terminalMet,Ser,Ala,Thr,Val,orGlyhavehalflivesgreaterthan20hours.ProteinswithN-terminalPhe,Leu,Asp,Lys,orArghavehalflivesof3minorlessN-endruleAprotein'shalf-lif3PESTproteinsIthasalsobeenfoundthatproteinsrichin

Pro(P),Glu(E),Ser(S)andThr(T),

called

PESTproteins,aremorerapidlydegradedthanotherproteins.PESTproteinsIthasalsobeen4UbiquitinUbiquitinisahighly-conserved,76residue(8.5kDa)proteinfoundwidelyineukaryotesProteinsaretaggedforselectivedestructionbyubiquitinAnisopeptidebondlinkstheterminalcarboxylofubiquitintothee-aminogroupofalysineresidueofa"condemned"protein.Threeenzymesareinvolved,designatedE1,E2&E3.UbiquitinUbiquitinisahighly5Protein-Degradation-and-教學(xué)講解課件Protein-Degradation-and-教學(xué)講解課件Proteasome20S

Largemultifunctionalproteasecomplexinthecytosolthatdegradesintracellularubiquitin-taggedproteins.(Justlikeabarrel)19S

regulatorysubunit(likeacap)This

regulatorycapcomplexrecognizesmulti-ubiquitinatedproteins,unfoldsthem,removesubiquitinchains,andprovidesapassagewayforthreadingunfoldedproteinsintothecorecomplex.26SProteasome20SLargemultifunct8Protein-Degradation-and-教學(xué)講解課件AAMetabolismAminoAcidDegradation1)Removalofthe-aminogroup

Deaminationi)L-AminoAcidOxidaseii)D-AminoAcidOxidaseiii)GlutamateDehydrogenase

TransaminationCombinedDeamination2)FatesofCskeletonketogenicaa&glycogenicaa3)DetoxificationandExcretionofAmmoniaAminoAcidSynthesisAAMetabolismAminoAcidDegrad10L-AminoAcidOxidase

L-aminoacidoxidase

isanenzymeinvolvedinaminoacidcatabolism.Itisaflavoprotein-containingenzymethatcatalyzesthereactionbelow,yieldingahydrogenperoxideintermediate.L-AminoAcidOxidaseL-amino11Protein-Degradation-and-教學(xué)講解課件GlutamatedehydrogenaseATP,GTPpromoteADP,GDPactivateGlutamatedehydrogenaseATP,GTTransaminase

Transaminaseisanameforacategoryofenzymesinvolvedinexchangeofanoxygenfroman-ketoacid(suchas-ketoglutarate)andanaminefromanaminoacid.Aminotransferasesutilizeacoenzyme－pyridoxalphosphateGPT&GOT

Notallaminoacidsundergotransamination(Thr,Pro,lys)TransaminaseTransaminaseis14TransaminasesLysinesidechainPyridoxalphosphateTransaminasesLysinesidechainTransamination

NH2|+HOOC-CH-R

O||HOOC-C-R

O||+HOOC-C-R

NH2|HOOC-CH-RTransaminationN16Protein-Degradation-and-教學(xué)講解課件Anexample-GOTAnexample-GOT18AminoAcid“X”

+-KetoglutarateGlutamate+-KetoAcid“X”-Ketoglutarate+NH4++NAD(P)HCombinedDeamination

TransaminationGlutamateDehydrogenase+NAD(P)+

AminoAcid“X”+-Ketog19FatesofC

skeletonGlucogenicKetogenic:Leu&LysBothglucogenicandketogenic:

Trp,Thr,Tyr,Ile,Phe(tttip)FatesofCskeletonGlucogenic20Protein-Degradation-and-教學(xué)講解課件MetabolicfatesofaminogroupsDietaryproteinCellularproteinAminoacidsCarbonskeletonNH4+Metabolicfatesofaminogroup22FatesofAmmoniumIonDirectexcretionAsn(Asn

synthetase)-inPlantsGln(Glnsynthetase)-inAnimalsUreaoruricacidFatesofAmmoniumIonDirectex23Glutaminesynthetase

-GenerationofBiologicallyActiveAmideNitrogen

GlutaminesynthetaseisadodecamerInanimals,theenzymeisakeyparticipantindetoxifyingammonia,

particularlyinthebrain,andinammoniaexcretioninthekidney.Accumulationofglutamateandglutaminedepletesa-ketoglutarate,

whichwouldinterferewiththecitricacidcycle.Glutaminesynthetaseistightlyregulated.Theamidenitrogenofglutamineisusedforthesynthesisofseveral

aminoacids,purineandpyrimidinenucleotides,andaminosugarsGlutaminesynthetaseGlutamineProtein-Degradation-and-教學(xué)講解課件RegulationofglutaminesynthetaseAllostericrergulation:

CumulativefeedbackInhibition

Eightspecificfeedbackinhibitors,whichareeithermetabolicendproducts

ofglutamine(tryptophan,histidine,glucosamine-6-phosphate,carbamoyl

phosphate,CTP,orAMP)orindicatorsofthegeneralstatusofaminoacid

metabolism(alanineorglycine)Bindtoanyofthesubunitsoftheenzymeandatleastpartiallyinhibitit.

Themoreinhibitorsthatbind,thegreatertheinhibition.Covalentmodification:

adenylylationregulatoryproteinPIIUT:stimulatedbyATP&a-ketoglutarate;inhibitedbyglutamineTyr397inactivatedRegulationofglutaminesyntheRegulationoftheactivityofE.coliglutaminesynthetase.GS:GlutaminesynthetaseAT:AdenylyltransferaseUT:UridylyltransferasePII:RegulatoryproteinRegulationoftheactivityofNitrogenexcretionNH4+UricacidUrea+uricacidNitrogenexcretionNH4+Uricaci28Protein-Degradation-and-教學(xué)講解課件Protein-Degradation-and-教學(xué)講解課件Protein-Degradation-and-教學(xué)講解課件RegulationoftheureacycleRegulationoftheureacycle32AminoAcidBiosynthesisPlantsandmicroorganismscanmakeall20aminoacidsandallotherorganismsneedNmetabolitesIntheseorganisms,glutamateisthesourceofN,viatransamination(aminotransferase)reactionsMammalscanmakeonly10ofthe20aminoacidsTheothersareclassedas"essential"aminoacidsandmustbeobtainedinthedietAllaminoacidsaregroupedintofamiliesaccordingtotheintermediatesthattheyaremadefromAminoAcidBiosynthesisPlants33Protein-Degradation-and-教學(xué)講解課件EssentialAminoAcidsAnyaminoacidforwhichthecorresponding-ketoacidisnotavailableasanintermediateofcarbohydratemetabolism.EssentialAminoAcidsAnyamino35ProteinDegradation&AAMetabolismProteinDegradation&AAMetab36ProteindegradationExtracellulardegradationIntracellulardegradation

ATP-independentoccursinlysosomes

ATP-dependent

i)N-endruleand“PEST”sequenceii)TheroleofUbiquitin(泛素）

iii)Proteasome（蛋白酶體）

iiii)HighlyregulatedProteindegradation37N-endruleAprotein's

half-life

correlateswithits

N-terminalresidue.ProteinswithN-terminalMet,Ser,Ala,Thr,Val,orGlyhavehalflivesgreaterthan20hours.ProteinswithN-terminalPhe,Leu,Asp,Lys,orArghavehalflivesof3minorlessN-endruleAprotein'shalf-lif38PESTproteinsIthasalsobeenfoundthatproteinsrichin

Pro(P),Glu(E),Ser(S)andThr(T),

called

PESTproteins,aremorerapidlydegradedthanotherproteins.PESTproteinsIthasalsobeen39UbiquitinUbiquitinisahighly-conserved,76residue(8.5kDa)proteinfoundwidelyineukaryotesProteinsaretaggedforselectivedestructionbyubiquitinAnisopeptidebondlinkstheterminalcarboxylofubiquitintothee-aminogroupofalysineresidueofa"condemned"protein.Threeenzymesareinvolved,designatedE1,E2&E3.UbiquitinUbiquitinisahighly40Protein-Degradation-and-教學(xué)講解課件Protein-Degradation-and-教學(xué)講解課件Proteasome20S

Largemultifunctionalproteasecomplexinthecytosolthatdegradesintracellularubiquitin-taggedproteins.(Justlikeabarrel)19S

regulatorysubunit(likeacap)This

regulatorycapcomplexrecognizesmulti-ubiquitinatedproteins,unfoldsthem,removesubiquitinchains,andprovidesapassagewayforthreadingunfoldedproteinsintothecorecomplex.26SProteasome20SLargemultifunct43Protein-Degradation-and-教學(xué)講解課件AAMetabolismAminoAcidDegradation1)Removalofthe-aminogroup

Deaminationi)L-AminoAcidOxidaseii)D-AminoAcidOxidaseiii)GlutamateDehydrogenase

TransaminationCombinedDeamination2)FatesofCskeletonketogenicaa&glycogenicaa3)DetoxificationandExcretionofAmmoniaAminoAcidSynthesisAAMetabolismAminoAcidDegrad45L-AminoAcidOxidase

L-aminoacidoxidase

isanenzymeinvolvedinaminoacidcatabolism.Itisaflavoprotein-containingenzymethatcatalyzesthereactionbelow,yieldingahydrogenperoxideintermediate.L-AminoAcidOxidaseL-amino46Protein-Degradation-and-教學(xué)講解課件GlutamatedehydrogenaseATP,GTPpromoteADP,GDPactivateGlutamatedehydrogenaseATP,GTTransaminase

Transaminaseisanameforacategoryofenzymesinvolvedinexchangeofanoxygenfroman-ketoacid(suchas-ketoglutarate)andanaminefromanaminoacid.Aminotransferasesutilizeacoenzyme－pyridoxalphosphateGPT&GOT

Notallaminoacidsundergotransamination(Thr,Pro,lys)TransaminaseTransaminaseis49TransaminasesLysinesidechainPyridoxalphosphateTransaminasesLysinesidechainTransamination

NH2|+HOOC-CH-R

O||HOOC-C-R

O||+HOOC-C-R

NH2|HOOC-CH-RTransaminationN51Protein-Degradation-and-教學(xué)講解課件Anexample-GOTAnexample-GOT53AminoAcid“X”

+-KetoglutarateGlutamate+-KetoAcid“X”-Ketoglutarate+NH4++NAD(P)HCombinedDeamination

TransaminationGlutamateDehydrogenase+NAD(P)+

AminoAcid“X”+-Ketog54FatesofC

skeletonGlucogenicKetogenic:Leu&LysBothglucogenicandketogenic:

Trp,Thr,Tyr,Ile,Phe(tttip)FatesofCskeletonGlucogenic55Protein-Degradation-and-教學(xué)講解課件MetabolicfatesofaminogroupsDietaryproteinCellularproteinAminoacidsCarbonskeletonNH4+Metabolicfatesofaminogroup57FatesofAmmoniumIonDirectexcretionAsn(Asn

synthetase)-inPlantsGln(Glnsynthetase)-inAnimalsUreaoruricacidFatesofAmmoniumIonDirectex58Glutaminesynthetase

-GenerationofBiologicallyActiveAmideNitrogen

GlutaminesynthetaseisadodecamerInanimals,theenzymeisakeyparticipantindetoxifyingammonia,

particularlyinthebrain,andinammoniaexcretioninthekidney.Accumulationofglutamateandglutaminedepletesa-ketoglutarate,

whichwouldinterferewiththecitricacidcycle.Glutaminesynthetaseistightlyregulated.Theamidenitrogenofglutamineisusedforthesynthesisofseveral

aminoacids,purineandpyrimidinenucleotides,andaminosugarsGlutaminesynthetaseGlutamineProtein-Degradation-and-教學(xué)講解課件RegulationofglutaminesynthetaseAllostericrergulation:

CumulativefeedbackInhibition

Eightspecificfeedbackinhibitors,whichareeithermetabolicendproducts

ofglutamine(tryptophan,histidine,glucosamine-6-phosphate,carbamoyl

phosphate,CTP,orAMP)orindicatorsofthegeneralstatusofaminoacid

metabolism(alanineorglycine)Bindtoanyofthesubunitsoftheenzymeandatleastpartiallyinhibitit.

Themoreinhibitorsthatbind,thegreatertheinhibition.Cov