What does Km represent in enzymology?

Km, or the Michaelis constant, is a crucial parameter in enzymology that represents the substrate concentration at which an enzyme-catalyzed reaction reaches half of its maximum velocity (Vmax). More specifically, Km is indicative of the enzyme's affinity for its substrate. A low Km value suggests a high affinity, meaning the enzyme can effectively bind its substrate even at low concentrations. Conversely, a high Km indicates a lower affinity, as higher concentrations of substrate are required to achieve the same half-maximal reaction rate.

This concept is fundamental in understanding how enzymes interact with substrates and how they can be affected by factors such as competitive inhibition. It gives insight into enzyme behavior in different physiological conditions and is key for both basic and applied biochemistry. Understanding Km allows researchers and biochemists to predict how changes in substrate concentration will affect enzyme activity, which is vital in fields such as drug development and metabolic engineering.