1. ENZYME KINETICS

2. catalyzed uncatalyzed 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? amount of enzyme 4x 2x 1x amount of substrate 8x 4x 2x 1x [P] time

6. V [S] 1/2 V max KmKm V max

7. 1/V -1/K m 1/[S] 1/V max

8. V max /K m V/[S] V V max

9. An example of the three plotting methods using some hypothetical data and Excel to make the graphs: Michaelis-Menten V max = 45 - 50 (?) K m = 2.5 - 3 (depending on V max )

10. (I used Excel’s functions to get the slope and the y intercept and then calculated K m and V max from those values.)

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

14. 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 (V max ), the concentration of substrate ([S]), and the affinity of the enzyme for substrate (K m ). V max and K m 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, K m provides an indication of the affinity of an enzyme for its substrate. “Turnover number” and “Catalytic efficiency” provide even better measures of enzyme activity.