The Inhibition of Lactate Dehydrogenase by 3-Acetylpyridine Adenine Dinucleotide and Bisulfite

The kinetics and mechanism of action of a synergistic inhibition of lactate dehydrogenase by bisulfite and 3-acetylpyridine adenine dinucleotide were investigated. The inhibition, which was competitive to NADH in the forward reaction, occurred with all hybrids of the enzyme, the muscle type being the least sensitive. The mechanism of inhibition appeared to involve binding of the 3-acetylpyridine moiety of the dinucleotide to a site on the enzyme by a bisulfite molecule. Spectral evidence with the reduced coenzyme analogue and the reduced mononucleotide suggested that the site affected was on the pyridine moiety of the nucleotide.