QUANTIFYING THE POSITION OF THE STATIONARY STATE TRAJECTORY BETWEEN THE MICHAELIS-MENTEN AND BRIGGS-HALDANE EQUATIONS AS A FUNCTION OF THE INITIAL ENZYME CONCENTRATION

Abstract

For single intermediate enzyme kinetic systems, a relationship between a defined dimensionless parameter alpha (α) and the rate constants and initial enzyme concentration of the system was derived to describe the stationary-state trajectory of d(P)/dt versus (S) between the upper and lower bounds of the Michaelis-Menten and Briggs-Haldane systems. It was found that α is a function of E _o /k _m and the parameter Ω, which is a function of k ₂ and k ₃. The development of the α parameter provides a new method for directly estimating all the rate constants in the enzyme kinetic model, given (S) and (P) data as a function of time. This method for estimating the three rate constants and initial enzyme concentration is tested on four sets of simulated discrete (isothermal) data covering a range of different trajectories and on experimental data for the horseradish-peroxidase enzyme system.

Keywords:

• Briggs-Haldane equation
• Enzyme kinetics
• Estimating rate constants
• Michaelis-Menten equation
• Stationary-state trajectory