Studies of Baker's yeast metabolism: III. Oxidation of acetaldehyde

Abstract

The kinetics of respiration and pyridine nucleotide reduction during acetaldehyde oxidation by baker's yeast have been studied. While a concentration of 0.11 m acetaldehyde causes a half-maximal saturation of the respiratory system, higher concentrations cause a reversible inhibition of respiration. Titration studies of oxygen with low concentrations (0.5 m and lower) of acetaldehyde indicate that most of the aldehyde is oxidized, presumably by a DPN-linked dehydrogenase to acetic acid, while the remainder may be reduced to ethanol in short-term experiments. In experiments of longer duration the aldehyde tends to be oxidized completely. The reducing equivalents generated in the oxidation of acetaldehyde to acetic acid are capable of activating oxidative phosphorylation. Acid that is produced by oxidation of acetaldehyde yields hydrogen ions that permeate out of the cell in stoichiometric exchange with extracellular potassium which permeates into the cell.