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Enzyme Catalysis (26.4)

Enzyme Catalysis (26.4). Enzymes are catalysts, so their kinetics can be explained in the same fashion Rate law for enzyme catalysis is referred to as the Michaelis-Menten rate law K m is called the Michaelis constant

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Enzyme Catalysis (26.4)

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  1. Enzyme Catalysis (26.4) • Enzymes are catalysts, so their kinetics can be explained in the same fashion • Rate law for enzyme catalysis is referred to as the Michaelis-Menten rate law • Km is called the Michaelis constant • When the substrate concentration is very large, the rate depends only on the concentration of enzyme and the turnover rate (k2) • Equilibrium between reactants and enzyme-substrate complex (ES) is pushed to the right (i.e., only ES exists, no free enzyme) • When [S] >> Km, the maximum rate is achieved (Rmax) • One can get Km by realizing that it is equal to [S] when the rate is half of the maximum rate • If Km is small, then the enzyme tightly binds the substrate (equilibrium is shifted to ES)

  2. Rmax and Km (26.4) • Constants from Michaelis-Menten equation give insight into qualitative and quantitative aspects of enzyme kinetics • Indicate if enzyme inhibition is present and what type of inhibition is exhibited • Rmax is the maximum possible rate of conversion of substrate to product for a given enzyme • Km is related to how tightly an enzyme binds a substrate (the higher the value, the less tightly bound the substrate) • Inverting the Michaelis-Menten rate law gives an equation that can be useful for obtaining the maximum rate and the Michaelis constant • Lineweaver-Burk plot is generated by plotting 1/rate vs. 1/[S] • Lineweaver-Burk equation is more useful for getting constants since experiments can be done over a short range of substrate concentrations • y-intercept gives us Rmax, which is then used with the slope to get Km

  3. Enzymes as Catalysts

  4. Michaelis-Menten Plot for Catalyzed Reaction of CO2 with H2O

  5. Lineweaver-Burk Plot for Catalyzed Reaction of CO2 with H2O

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