Liver alcohol dehydrogenase: substrate inhibition and competition between substrates

Area of Science:

• Biochemistry
• Enzymology
• Chemical Kinetics

Background:

• Horse liver alcohol dehydrogenase (LADH) is an NAD-dependent enzyme catalyzing alcohol oxidation.
• High alcohol concentrations can inhibit LADH activity, complicating kinetic analysis.

Purpose of the Study:

• To derive and validate kinetic models for LADH that account for substrate inhibition.
• To develop a velocity expression for simultaneous presence of multiple alcohol substrates.
• To predict the effects of alcohol interactions on LADH activity.

Main Methods:

• Derivation of an initial velocity expression incorporating substrate inhibition and an ordered bimolecular mechanism.
• Testing the derived equation with ethanol, 1-butanol, and 1-hexanol.
• Derivation of a second velocity expression for competitive alcohol substrates.
• Validation of the second equation using competitive inhibition experiments.

Main Results:

• The initial velocity equation accurately predicted experimental velocities for single alcohol substrates.
• The derived equations showed excellent agreement with experimental data for competitive alcohol substrates.
• LADH mechanism remains consistent even with multiple substrates present.

Conclusions:

• The developed kinetic models effectively describe LADH activity under various substrate conditions.
• These equations provide a predictive tool for understanding alcohol interactions with LADH.
• The study confirms the robustness of the LADH oxidation mechanism.