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1、Chapter6Enzymecatalysis★Studyhistory,★Generalfeatures,★Classification,★Chemicalnature,★Kinetics★Mechanism,★RegulationThiswillbelecturedbyProfessorZengyiChangonApril21and28intheyear2007.ThestudyhistoryofenzymesEnzymes:Biologicalcatalyststhatpromoteandspeedupchemicalre
2、actionswithoutthemselvesbeingaltered(consumed)intheprocess.Theydeterminethepatternsoftransformationsforchemicals,aswellasformsofenergyinthelivingorganisms.Thediscoveryofenzymesasthebiocatalysts(1)Bothenzymologyandbiochemistrywereevolvedfromthe19thcenturyinvestigation
3、onthenatureofanimaldigestionandfermentation.Biochemicalreactionscouldnotbereproducedinthelabinitiallyandwasthought(e.g.,LouisPasteur)tooccurbytheactionofa“vitalforce”.Theideaof“catalyticforce”or“contactsubstance”promotingfermentationwasintroducedinabout1830s.Addition
4、ofalcoholtoanaqueousextractofmalt(geminatingbarley)andsalivaprecipitatedaflocculent(絮状)materialwhichliquefiedstarchpasteandconverteditintosugar,thismaterialwasnameddiastase(1833)(lateramylase淀粉酶).Thediscoveryofenzymesasthebiocatalysts(2)Pepsinwasdiscoveredastheactiv
5、eprincipleintheacidextractofgastricmucosacausingthedissolutionofcoagulatedeggwhite(1834).Other“solubleferments”discoveredinthe19thcenturyincludetrypsin(1857),invertin(laterinvertaseandsucrase,1864),papain(“vegetabletrypsin”,1879),etc.“Enzyme(somethinginyeast)”wasfirs
6、tcoinedforsuch“unorganizedferments”byKühnein1876.Enzymesforalcoholicfermentationwerefoundtobeactiveincellfreeextractsofyeast(1897,EduardBuchner):fermentationisachemicalprocess,nota“vitalprocess”.Thediscoveryofenzymesasthebiocatalysts(3)Relationshipofinitialvelocity(V
7、0)andsubstrateconcentration(S)wasexamined.Amathematicaldescriptionwasestablishedforthekineticsofenzymeaction(MichaelisandMenten,1913).Weak-bondinginteractionsbetweentheenzymesandtheirsubstrateswereproposedtodistortthesubstrateandcatalyzeareaction(Haldane,1930s).JohnB
8、urdonSandersonHaldane(1892-1964)LeonorMichaelis(1875-1949)MaudMenten(1879-1960)AGermanACanadianABritishGeneticistBeforeitwasknownth
