最新己糖激酶教学讲义PPT课件.ppt

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1、己糖激酶Thechemistryofglucosecatabolismwaselucidatedoverabout100yearsTheanaerobicbreakdown(fermentation)ofglucosetoethanolandCO2byyeasthasbeenexploitedformanycenturiesinbakingandwinemaking.Scientificinvestigationofthechemistryofglucosebreakdownbeganinthemid-19thcentury.Thecompletepa

2、thwaywasdescribedaround1940.D-glucoseoccupiesacentralpositioninmetabolismNADPH+(fat)OtherbiomoleculesThemetabolicfatesofglucoseinvolveshundredsorthousandsofchemicaltransformations.CO2+H2OD-glucoseG'o=–2840kJ/moleATPBiosynthesis?Thewholepathwayofglycolysis(arbitrarilydefinedasfr

3、omglucosetopyruvate)containingtenstepsofchemicalreactionswitheachcatalyzedbyaspecificenzyme,waselucidatedbythe1940s.GlucoseisfirstphosphorylatedatC-6:consumingATP(Presentinallcellsofallorganisms)Mg2+ATP2-istheactualsubstrateAnexergonicgrouptransferringreaction己糖激酶Glucoseisthustr

4、appedanddestabilized.Hexokinaseexhibitsinducedfitproperty:Thebindingofglucoseintheactivesitecausesamajorconformationalchange.InactiveconformationActiveconformationGlucoseSubstrate-inducedcleftclosingisageneralfeatureofallkinases!Glucose6-Pisthenconvertedtofructose6-P:viaisomeriz

5、ationAreversibleIsomerizationreaction(intramolecularredoxreaction)AnaldoseAketose磷酸己糖异构酶Anecessarypreludeforthenexttwostepsofreactions(phosphorylationandC-Ccleavage).Fructose6-PisthenphosphorylatedatC-1:ATPconsumingAnotherexergonicgrouptransferringreaction(PFK-1)磷酸果糖激酶-1Thesix-c

6、arbonfructose1,6-bisphosphateisthencleavedintotwodifferenttriosephosphatesThe“lysis”step123456醛缩酶Interconversionbetweendihydroxyacetonephosphateandglyceraldehyde3-Pthenoccurs(C3orC4)(C5orC2)(C1orC6)Otherhexoses(e.g.,Fru.,Man.,Gal.)arealsoconvertedtoglyceraldehyde3-phosphatetoent

7、erglycolysis.AreversibleIsomerizationreaction(intramolecularredoxreaction)磷酸丙糖异构酶AnaldoseAketoseGlyceraldehyde3-Pisthenoxidizedtoform1,3-bisphosphoglycerateOxidation(dehydrogenation)followedbyphosphorolysisAnacylphosphate(atypeofanhydride)3-磷酸甘油醛脱氢酶3H32P32P3HTetramericACysresidu

8、eisinvolvedinthecatalysisofglyceraldehyde3-Pdeh