Kinetic Parameters: $K_m$ and $V_{max}$
| Parameter | Core Concepts |
|---|---|
| $K_m$ | The concentration of substrate $[S]$ at which the reaction velocity $v = \frac{1}{2}V_{max}$. It serves as an inverse measure of enzyme-substrate affinity ($high$ $K_m$ $=$ $low$ $affinity$). |
| $V_{max}$ | The maximum reaction velocity when the enzyme is saturated with substrate ($[S] \gg K_m$). It is directly proportional to the total concentration of the enzyme ($[E]_t$). |
High-Yield Kinetic Associations:
- Competitive Inhibition: Increases $K_m$ (requires more substrate to compete) but does not change $V_{max}$.
- Noncompetitive Inhibition: Decreases $V_{max}$ (effectively reduces total enzyme concentration) but does not change $K_m$.
- Hexokinase ($low$ $K_m$, $low$ $V_{max}$): Efficient glucose uptake even at low blood glucose levels; found in most tissues.
- Glucokinase ($high$ $K_m$, $high$ $V_{max}$): Liver glucose sensor; only becomes highly active when blood glucose levels are elevated.