Ukr.Biochem.J. 2012; Volume 84, Issue 3, May-Jun, pp. 95-110

On true and apparent Michaelis constants in enzymology. III. Is it linear dependence between apparent Michaelis constant and limiting rate and is it possible to determine the substrate constant value using this dependence?

S. O. Karakhim

Palladin Institute of Biochemistry, National Academy of Sciences of Ukraine, Kyiv;
e-mail: laserlab@biochem.kiev.ua

The Slater-Bonner method which is used for graphic determination of substrate constant (Ks) by linear dependence of apparent Michaelis constant (Kmapp) on the limiting rate (Vapp) of enzyme-catalysed reactions with activator participation has been critically analysed. It has been shown that although it is possible to record the mechanisms of such reactions as a scheme similar to Michaelis-Menten model which allow to find correlation Kmapp and Vapp as equation Kmapp = Ks + Vapp/k1[E]0 ([E]0 is a total enzyme concentration, k1 is a rate constant of enzyme-substrate complex formation from free enzyme and substrate) in order to calculate Ks and individual rate constants (k1, k-1), but this approach for investigation of all reactions with activator participation ought not to be used. The above equation is not obeyed in general, it may be true for some mechanisms only or under certain ratios of kinetic parameters of enzyme-catalysed reactions.

Keywords: , , , , ,


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