Question

Michaelis Menten Constant $\left(K_m\right)$ is equal to

• A. The rate of reaction
• B. The rate of enzymatic activity
• C. Substrate concentration at which the reaction attains half of its maximum velocity
• D. Substrate concentration at which the rate of reaction is maximum.

Answer 1

Answer: (C)

Substrate concentration at which the reaction attains half of its maximum velocity

$K_m$ or the Michaelis - Menten constant is defined as the substance concentration (expressed in moles/l) at which half - maximum velocity in an enzyme catalysed molecules $(i.e.50\%)$ are bound with the substrate molecules when the substrate concentration equals the $K_m$ value. It was given by Leonor Michaelis and Maud menten $\left(1913\right)$. $K_m$ value is a characteristic feature of a given enzyme.Its is a representative for measuring the strength of ES complex. A low $K_m$ value indicates a strong affinity between enzyme and substrate where as high $K_m$ value reflects a weak affinity between them. For majority of enzymes, the $K_m$ values are in the range of ${10}^{-5}$ to ${10}^{-2}$ moles.

So, the correct answer is 'Substrate concentration at which the reaction attains half of its maximum velocity'.