What does a higher Km value indicate about an enzyme's efficiency?

A higher Km value indicates lower efficiency of an enzyme. Km, or the Michaelis constant, is a measure of the substrate concentration required to reach half of the enzyme's maximum velocity (Vmax). When Km is high, it suggests that a higher concentration of substrate is needed for the enzyme to operate effectively. This implies that the enzyme has a lower affinity for the substrate, meaning it is less efficient in catalyzing the reaction at lower substrate concentrations.

In practical terms, an enzyme with a high Km means that it is less effective at binding the substrate under physiological conditions compared to an enzyme with a low Km. Therefore, while the enzyme can still catalyze the reaction, it does so less readily, requiring a greater concentration of substrate to achieve the same reaction rate. This is fundamental in understanding enzyme kinetics and the implications of Km on metabolic processes.