https://doi.org/10.1351/goldbook.M03892
The dependence of an initial
rate of reaction
upon the concentration of a
substrate
S that is present in large excess over the concentration of an enzyme or other
catalyst
(or
reagent
) E with the appearance of
saturation
behaviour following the Michaelis-Menten equation: ν=V [S]Km+[S] where ν is the observed initial rate, V is its limiting value at substrate
saturation
(i.e. [S]Km), and Km the substrate concentration when ν=V2. The definition is experimental, i.e. it applies to any reaction that follows an equation of this general form. The symbols Vmax or νmax are sometimes used for V. The parameters V and Km (the '
Michaelis constant
') of the equation can be evaluated from the slope and intercept of a linear plot of ν1 vs. [S]1 (a '
Lineweaver–Burk plot
') or from slope and intercept of a linear plot of ν vs. ν[S] ('Eadie–Hofstee plot'). A Michaelis–Menten equation is also applicable to the condition where E is present in large excess, in which case the concentration [E] appears in the equation instead of [S]. The term has sometimes been used to describe reactions that proceed according to the scheme: E+Sk1k1ESkcatProducts in which case Km=k1+kcatk1 (Briggs–Haldane conditions). It has more usually been applied only to the special case in which k1kcat and Km=k1k1=Ks; in this case Km is a true
dissociation
constant (Michaelis–Menten conditions).
See also:
rate-determining step
Sources:
PAC, 1994, 66, 1077. (Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994)) on page 1140 [Terms] [Paper]
PAC, 1996, 68, 149. (A glossary of terms used in chemical kinetics, including reaction dynamics (IUPAC Recommendations 1996)) on page 172 [Terms] [Paper]