Anion binding to liver alcohol dehydrogenase

Area of Science:

• Biochemistry
• Enzymology
• Protein-ligand interactions

Background:

• Liver alcohol dehydrogenase (LADH) is a crucial enzyme in alcohol metabolism.
• Understanding anion binding is vital for characterizing enzyme active sites and kinetics.
• Previous studies on LADH kinetics have not fully addressed buffer anion interference.

Purpose of the Study:

• To characterize complex formation at the general anion-binding site of LADH.
• To determine equilibrium dissociation constants for various anions.
• To assess the impact of buffer anions on coenzyme (NADH) binding kinetics.

Main Methods:

• Transient-state kinetic methods were employed.
• Nicotinamide adenine dinucleotide (NADH) served as a reporter ligand.
• Equilibrium dissociation constants were measured for anion binding.

Main Results:

• Anion binding affinity generally followed the lyotropic series, with notable high affinity for sulfate.
• Phosphate and pyrophosphate buffers showed negligible interaction at pH 8-10.
• Phosphate binding increased at lower pH but remained relatively weak (Kd ~60 mM).

Conclusions:

• The specific affinity for sulfate may be a characteristic of enzymic arginyl sites binding anions.
• Buffer anion binding is unlikely to significantly affect previously reported pH-dependence data for LADH coenzyme binding.
• New kinetic parameter estimates for NADH binding align with prior findings, validating the experimental conditions.