Michaelis-Menten constant

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The Michaelis-Menten describes and enzyme reaction and is as follows:

V= Vmax[S]/Km[S]

V = is the rate of the reaction

Vmax = is the maximal rate of the reaction

K= the concentration at which Vmax is 1/2

Using the Km, this equation is useful to tell the affinity an enzyme has for its substrate. If the Km is high, this means the concentration at which 1/2 Vmax is reached is high, so the affinity the enzyme has for its substrate is low (because a lot of substrate is needed to reach 1/2 Vmax). If Km is low, this means the affinity is high, because less substrate was needed to get to half the maximal rate of the reaction (Vmax)[1].


  1. Down, J.E and Riggs, D.S. 1965, A comparison of estimates of Michaelis-Menten kinetic constants from various linear transformations. The Journal of Biological chemistry. 240 (2),

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