Km of wn emzyme is
**Core Concept**
The Michaelis constant (Km) is a measure of the affinity of an enzyme for its substrate, representing the substrate concentration at which the enzyme reaches half of its maximal velocity (Vmax). It is an important parameter in enzyme kinetics, providing insight into the interaction between the enzyme and its substrate.
**Why the Correct Answer is Right**
The Km value is a reflection of the binding affinity between the enzyme and its substrate. A lower Km value indicates a higher affinity, meaning the enzyme can bind to the substrate more efficiently at lower concentrations. In the context of enzyme kinetics, Km is obtained from the Lineweaver-Burk plot, which is a graph of the reciprocal of velocity (1/V) against the reciprocal of substrate concentration (1/[S]). The Km value is then calculated from the x-intercept of the plot. The Km value is specific to each enzyme-substrate pair and provides valuable information about the enzyme's catalytic efficiency.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect as Km is not a unit of measurement. Km is typically expressed in units of concentration, such as millimolar (mM) or micromolar (μM).
**Option B:** This option is incorrect as Km is not a measure of enzyme activity. While enzyme activity is related to Km, Km specifically measures the substrate concentration at which the enzyme reaches half of its maximal velocity.
**Option C:** This option is incorrect as Km is not a measure of enzyme inhibition. While enzyme inhibition can affect Km, Km specifically measures the substrate concentration at which the enzyme reaches half of its maximal velocity.
**Clinical Pearl / High-Yield Fact**
A key point to remember is that Km is not a fixed value and can vary depending on the enzyme, substrate, and experimental conditions. Additionally, Km can be affected by enzyme inhibitors, which can alter the enzyme's binding affinity for its substrate.
**Correct Answer:** D. 5.6 mM