Effect of [S] on the V。of anEnzyme-Catalyzed Reaction.the plateau-like V。regionisclosetotheomaximum velocity,Vmax1VmKmSubstrate concentration, [S] (mm)
General Theory of Enzyme ActionProposedbyMichaelisandMenten.step1-enzymeandsubstratecombinetoformacomplexinareversible,relativelyfaststep:念E+SES(6-7)iA(6-8)ESE+PEstep2-thecomplexbreaksdowntoyieldthefreeenzymeandthereactionproductinaslowerstep:becausethesecondsteplimitstheoverall reactionrate, the overall rate isproportional to [Es]
The Saturation EffectVmax is observedwhenvirtuallyalltheoaenzymeispresentastheEScomplex-furtherincreases1Vmaxin [S] have noeffectonrateresponsibleforthe plateauKmobservedSubstrateconcentration,[S] (mm)
TheRelationshipbetweenSubstrateConcentrationandReactionRateCanBeExpressedwiththeMichaelis-MentenEquationthecurveexpressingtherelationshipbetween[S]andVcanbeexpressedbytheMichaelis-Mentenequation:Vmax[S](6-9)Vo=1Km+[S]whereVoistheinitialvelocity,Vmaxisthemaximumvelocity,[S]istheinitialsubstrateconcentration,andKmisaconstant calledthe Michaelis constant