Michaelis constant

(mi′kā·ləs ′kän·stənt)

(biochemistry) A constant K_m such that the initial rate of reaction V, produced by an enzyme when the substrate concentration is high enough to saturate the enzyme, is related to the rate of reaction v at a lower substrate concentration c by the formula V = v(1 + K_m/c).

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[Etymology: L. Michaelis; Germany, USA 1875-1949] biochemistry. Symbol K_m. If an enzyme reacts at rate V at saturation in a substrate but at rate v at sub-saturation concentration c, then

K_m = c(V - v)/v

which is identically the concentration when v = ½V.

(mĭ-kā'lĭs) or Michaelis-Men·ten constant (-mĕn'tən)
n.

A constant that is equal to the substrate concentration at which an enzyme reaction proceeds at half the maximum velocity.