Enzyme Kinetics Determined by Single-Injection Isothermal Titration Calorimetry

Area of Science:

• Biochemistry
• Enzyme Kinetics
• Biophysical Chemistry

Background:

• Enzyme kinetics are crucial for understanding biological processes.
• Traditional methods for determining enzyme kinetic parameters can be complex and time-consuming.
• Isothermal titration calorimetry (ITC) offers a label-free biophysical approach to study molecular interactions and reactions.

Purpose of the Study:

• To describe a method for collecting Michaelis-Menten kinetic data using ITC.
• To demonstrate the utility of the single-injection method with ITC for enzyme assays.
• To determine key enzyme kinetic parameters (K_m, k_cat, V_max) and thermodynamic data (Δ_rH) in a single assay.

Main Methods:

• Utilizing isothermal titration calorimetry (ITC) to measure heat rate.
• Employing a single-injection method for enzyme kinetic data collection.
• Analyzing the heat rate signal, which is directly proportional to the reaction rate.

Main Results:

• Successful collection of Michaelis-Menten kinetic data using ITC.
• Determination of enthalpy change (Δ_rH), K_m, k_cat, and V_max from a single assay.
• Demonstration that the method does not require enzyme labeling or immobilization.

Conclusions:

• Isothermal titration calorimetry combined with a single-injection method provides an efficient way to determine enzyme kinetic parameters.
• This label-free approach simplifies enzyme kinetic studies.
• The method is valuable for characterizing enzyme behavior and reaction thermodynamics.