9: Enzyme Kinetics
Students measure lactase reaction rates at different substrate concentrations, plot velocity data, and analyze how temperature, pH, or inhibitors affect enzyme activity in a laboratory setting.
Michaelis-Menten Constant (Km) from Enzyme Activity Data
Click to show Michaelis-Menten Constant (Km) from Enzyme Activity Data example problem
Michaelis-Menten question. The following question refers to the table (below) of enzyme activity.
| substrate concentration, [S] |
initial reaction velocity V0 |
|---|---|
| 0.001 | 12.8 |
| 0.002 | 23.4 |
| 0.005 | 46.7 |
| 0.010 | 70.0 |
| 0.020 | 93.4 |
| 0.050 | 116.7 |
| 0.100 | 127.3 |
| 0.200 | 133.4 |
| 0.500 | 137.3 |
| 1.000 | 138.7 |
| 2.000 | 139.4 |
| 5.000 | 139.8 |
| 10.000 | 139.9 |
| 20.000 | 140.0 |
Using the table (above), calculate the value for the Michaelis-Menten constant, KM.
Enzyme Inhibition Type from Enzyme Activity Data
Click to show Enzyme Inhibition Type from Enzyme Activity Data example problem
Michaelis-Menten Kinetics and Inhibition Type Determination
The table below presents data on enzyme activity measured as initial reaction velocities (V0) with and without the presence of an inhibitor at various substrate concentrations ([S]).
| substrate concentration, [S] |
initial reaction velocity no inhibitor V0 (–inh) |
initial reaction velocity with inhibitor V0 (+inh) |
|---|---|---|
| 0.001 | 16.7 | 13.4 |
| 0.002 | 28.6 | 20.0 |
| 0.005 | 50.0 | 28.6 |
| 0.010 | 66.7 | 33.4 |
| 0.020 | 80.0 | 36.4 |
| 0.050 | 91.0 | 38.5 |
| 0.100 | 95.3 | 39.3 |
| 0.200 | 97.6 | 39.7 |
| 0.500 | 99.1 | 39.9 |
| 1.000 | 99.6 | 40.0 |
| 2.000 | 99.8 | 40.0 |
| 5.000 | 100.0 | 40.0 |
Based on the data provided, determine the type of inhibition show by the inhibitor. Consider how the addition of the inhibitor affects the initial reaction velocities (V0) at various substrate concentrations ([S]).