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ENZYME KINETICS

ENZYME KINETICS. amount of enzyme. 4x 2x 1x. amount of substrate. catalyzed uncatalyzed. [P]. 8x 4x 2x 1x. time. time. time. Formation of product is faster in the catalyzed reaction than in

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ENZYME KINETICS

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  1. ENZYME KINETICS

  2. amount of enzyme 4x 2x 1x amount of substrate catalyzed uncatalyzed [P] 8x 4x 2x 1x time time time • Formation of product is faster in the catalyzed reaction than in • the uncatalyzed reaction and initially is linear with time. • We measure the enzyme activity by the rate of formation of product in the catalyzed reaction. • Enzyme activity is proportional to the amount of enzyme and increases with an increase in the amount of substrate added. • What more can we say about the enzyme and the reaction from the dependence of the reaction rate on the conditions?

  3. Vmax V 1/2 Vmax Km [S]

  4. 1/V 1/Vmax -1/Km 1/[S]

  5. Vmax V V/[S] Vmax/Km

  6. An example of the three plotting methods using some hypothetical data and Excel to make the graphs: Michaelis-Menten Vmax = 45 - 50 (?) Km = 2.5 - 3 (depending on Vmax)

  7. (I used Excel’s functions to get the slope and the y intercept and then calculated Km and Vmax from those values.)

  8. (Again, I used Excel’s functions to get the slope and the y intercept.)

  9. Summary • The reaction of an enzyme with its substrate to form product • can be described quantitatively: the reaction rate (V) depends • on the amount of enzyme (Vmax), the concentration of substrate • ([S]), and the affinity of the enzyme for substrate (Km). • Vmax and Km can be determined by measuring V as a function • of [S]. There are several methods for plotting the results to get • Vmax and Km. • Under certain conditions, Km provides an indication of the affinity • of an enzyme for its substrate. “Turnover number” and “Catalytic • efficiency” provide even better measures of enzyme activity.

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