Although the Michaelis-Menten(MM) equation as the basic equation of enzyme reaction kinetics was developed more than 100 years ago, further studies to validate the equation are still ongoing, and the upper limit of enzyme concentration for accurate estimation of the parameters involved in this equation has not yet been fully determined.
We have extensively investigated the correlation between the simultaneous ordinary differential equations for monosubstrate irreversible enzyme reaction (HMM system) and its approximate MM equation by means of numerical simulation, focusing on the relationship between initial enzyme concentration ([E]0) and Michaelis constant (Km).
According to the investigation, at [E]0<Km, the initial reaction rate v0 still becomes a function of the initial substrate concentration [S]0. This function is identical to the MM equation at [E]0 ≤ 0.01Km, but is described by a new expression at 0.01 Km ≤ [E]0 < Km. The function is of significance in enzyme assays as a comprehensive approximate formula for the HMM system.
The results have been published in the journal "Biochimie" under the title of "Relationship between Enzyme Concentration and Michaelis Constant in Enzyme Assays" (https://doi.org/10.1016/j.biochi.2020.06.002).
