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中南大学生物化学考研课件ch15酶的特性和调控enzymespecificityandregulation06.ppt

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BiochemistryContentsEnzymespecificityTherearetwomodelsofbindingofasubstratetoanenzymeTheinducedfitmodel(ex.ofhexokinase)SubstrateishighlyspecifictoitsenzymeQuestion: Pleasecomparethedifferenceinmechanismofspecificityamongtheserineproteasestrypsin,chymotrypsinandelastase.请比较丝氨酸胰蛋白酶、胰凝乳蛋白酶、弹性蛋白酶在特异性机制的区别CarbamidineControlofenzymeactionFeedbackregulation反馈调控 Reversiblenoncompetitiveinhibition可逆非竞争抑制 FeedbackregulationisusuallyaccompaniedbyAllostericaction反馈调控通常伴随着变构作用 Reversiblecovalentmodification可逆共价修饰 Themostcommon:Phosphorylationanddephosphorylation最典型:磷酸化和去磷酸化 Irreversiblemodificationofproenzymes酶原的非可逆修饰 Exampleofallostericcontrolandcovalentmodification变构调控和共价修饰的例子FeedbackregulationExampleofallostericregulationAplotofV0against[S]issigmoidcurve,ratherthanthehyperbolicplotspredictedbytheMichaelis-Mentenequation. Substratebindingiscooperative底物键合作用是协同性的 TwokindsofFactorsbindingtotheregulatorysubunits allostericactivator allostericinhibitorTwotypesofallostericeffectors两种变构效应剂Twomodelsofallostericmodification两种变构修饰模型AdimericproteincanexistineitheroftwoconformationalstatesatequilibriumHeterotropiceffectors allostericactivator:bindstoRstate allostericinhibitor:bindstoTstateReversiblecovalentmodification可逆的共价修饰PhosphorylationanddephosphorylationIrreversiblemodificationofproenzymesorbeingzymogens酶原的非可逆修饰ZymogenisactivatedbyproteolyticcleavageofitspeptidebondsExampleofallostericcontrolandcovalentmodification----GlycogenmetabolismGlycogenmetabolism糖原代谢(1)Glycogendegradation糖原分解Glycogensynthesiscatalyzed byglycogensynthase(p757)ThemechanismofcovalentmodificationandallostericregulationofglycogenphosphorylaseGlycogenphosphorlyaseandglycogensynthasecanbesimultaneouslyregulatedbyproteinkinaseACovalent modificationActivationofproteinKinaseAstimulatedbyhomoneHomework