Formulation of a universal first-order rate constant for enzymatic reactions

Area of Science:

• Biochemistry
• Enzymology
• Chemical Kinetics

Background:

• Enzymatic reactions are frequently analyzed using a first-order rate constant, k(cat)[E]₀/K(m).
• This approach assumes total enzyme concentration [E]₀ is the limiting factor.
• However, this approximation has critical limitations in accurately describing enzyme kinetics.

Purpose of the Study:

• To identify the shortcomings of using k(cat)[E]₀/K(m) in enzymatic reaction analysis.
• To propose a more universally applicable first-order rate constant for enzyme kinetics.
• To enable accurate determination of catalytic and binding contributions to enzyme rate constants.

Main Methods:

• Analysis of the limitations of the k(cat)[E]₀/K(m) approximation.
• Derivation and proposal of a new first-order rate constant: k(cat)[ES](K)/[S]₀.
• Simulation of enzymatic reactions under various conditions using the proposed rate constant.

Main Results:

• Demonstration that k(cat)[E]₀/K(m) is only valid under highly restricted conditions.
• Introduction of k(cat)[ES](K)/[S]₀, derived from initial equilibrium concentration of the enzyme-substrate complex [ES](K).
• Validation of k(cat)[ES](K)/[S]₀ for simulating enzymatic reactions across a broad range of experimental parameters.

Conclusions:

• The conventional k(cat)[E]₀/K(m) is insufficient for comprehensive analysis of enzyme kinetics.
• The proposed rate constant k(cat)[ES](K)/[S]₀ provides a more robust and universally applicable method.
• This new constant facilitates precise evaluation of enzyme catalytic efficiency and substrate binding under all conditions.