Final answer:
The Michaelis-Menten constant (Km) represents the substrate concentration at which the reaction velocity is half of the enzyme's maximal velocity (Vmax).
Step-by-step explanation:
The measurement of the enzyme-substrate relationship equal to the substrate concentration that gives ½ of the maximal velocity of the catalyzed reaction is given by the Michaelis-Menten constant, abbreviated as Km. The Km value is a fundamental parameter in enzymology that indicates how much substrate is needed to achieve half of the enzyme's maximum reaction velocity (Vmax).
It represents a point on the enzyme saturation curve where half of the enzyme's active sites are occupied by the substrate, which can be visualized on a Michaelis-Menten plot. At this specific substrate concentration, the velocity of the enzyme-catalyzed reaction is exactly one-half of Vmax; hence it can be described by the equation V = ½Vmax. The Michaelis-Menten constant is crucial because it provides insights into the enzyme's affinity for the substrate, where a lower Km indicates a higher affinity.