Why substrate depletion has apparent first-order kinetics in enzymatic digestion.

Area of Science:

• Biochemistry
• Chemical Kinetics
• Enzymology

Background:

• Enzyme digestion assays frequently exhibit apparent first-order kinetics.
• Four potential explanations for this kinetic behavior exist, including limiting steps or pseudo-first-order conditions.
• Understanding the precise kinetics is crucial for interpreting experimental results.

Purpose of the Study:

• To investigate the kinetics of protein digestion.
• To formulate rate equations for proposed digestion mechanisms (one-by-one and zipper).
• To explain why apparent first-order kinetics are observed in protein digestion.

Main Methods:

• Formulation of rate equations for two distinct protein digestion mechanisms.
• Mathematical analysis of kinetic behavior under varying substrate and enzyme concentrations.
• Comparison of theoretical predictions with experimental observations.

Main Results:

• Protein digestion exhibits apparent first-order kinetics across both investigated mechanisms.
• This kinetic behavior is consistent when initial substrate concentration is low relative to initial enzyme concentration.
• The study provides a theoretical basis for observed experimental data.

Conclusions:

• Apparent first-order kinetics in protein digestion are mechanism-independent under specific conditions.
• The findings offer explanations for experimental observations in enzyme digestion assays.
• A novel experimental protocol is proposed to elucidate protein digestion mechanisms.