The 'double' Michaelis-Menten equation: estimation of parameters

Area of Science:

• Biochemistry
• Enzyme kinetics
• Transport processes

Background:

• Enzymic reactions and transport processes often exhibit complex kinetics.
• The Michaelis-Menten model is a cornerstone for describing enzyme kinetics.
• Dual Michaelis-Menten models are necessary for certain complex biological systems.

Purpose of the Study:

• To develop a reliable method for obtaining kinetic data from assays with high substrate consumption.
• To validate an approximation for calculating substrate concentration in dual Michaelis-Menten systems.
• To assess the accuracy of this approximation under various kinetic parameter ratios.

Main Methods:

• Modeling the concentration dependence using the sum of two Michaelis-Menten terms.
• Calculating data pairs of average reaction rate and corresponding substrate concentration.
• Approximating the instantaneous substrate concentration using a simplified Michaelis-Menten approach.

Main Results:

• Reliable kinetic data can be obtained even when up to 70% of the substrate is consumed.
• The approximated substrate concentration shows a relative error not exceeding 5% up to 50% substrate consumption.
• The error remains below 10% even with 70% substrate consumption under tested parameter ranges (1 ≤ K2/K1 ≤ 10^5, 10^-2 ≤ V2/V1 ≤ 10^2).

Conclusions:

• A simplified calculation method provides accurate substrate concentration estimations for dual Michaelis-Menten kinetics.
• This method enhances the reliability of kinetic data acquisition in assays with substantial substrate depletion.
• The findings are applicable to both enzymic reactions and transport processes described by two Michaelis-Menten terms.