What is the Difference Between Km and Vmax?

Km and Vmax are two important parameters used in the field of biochemistry to describe the behavior of enzymes. They provide different information about the reaction:

• Km: This is the substrate concentration at which half of the maximum velocity is achieved. It is a measure of the enzyme's affinity for its substrate. A low Km value indicates a high affinity of the enzyme for its substrate, while a high Km value indicates a low affinity. Km is used to interpret changes in the reaction rate with changes in substrate concentration.
• Vmax: This is the maximum reaction velocity at which all enzymes become saturated with substrate. Vmax represents the maximum rate at which an enzyme can catalyze a reaction. It is expressed in units of velocity or reaction rate (e.g., millimoles per liter per minute) and is dependent on the number of active enzyme molecules present.

Both Km and Vmax can be determined by plotting a graph of the rate of reaction (v) against the concentration of substrate (S), as described by the Michaelis-Menten equation. Km is the concentration of substrate that permits the enzyme to achieve half Vmax.

Comparative Table: Km vs Vmax

The Michaelis-Menten equation is used to describe enzyme kinetics and provides information about the maximum enzyme velocity (Vmax) and the Michaelis-Menten constant (Km). Here is a table summarizing the key differences between Km and Vmax:

To calculate Vmax and Km, researchers often use a Lineweaver-Burk plot, which is derived from the Michaelis-Menten equation. This plotting technique involves transforming curved data into straight lines by plotting the reciprocal of substrate concentration vs. the reciprocal of enzyme velocity. Once the data is plotted in this manner, researchers can determine the Km and Vmax values by analyzing the intercepts and slope of the Lineweaver-Burk plot.