Biological production of acid and alkali. 2. A redox theory for the process in yeast with application to the production of gastric acidity

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Abstract
When organic acid (succinic), or free H+ in exchange for K+, is excreted by fermenting yeast, H+ ions are removed from within the cell in amt. equivalent to the total titratable acid secreted. This accounts for the excess HCO3 ions formed when K exchanges for H, as compared with the control without KC1. The acid-secreting mechanism is almost entirely inhibited by 0.005-0.001 [image] azide. Ethanol production is increased by azide, and for every 2 equivalents of acid secreted about 1 extra mol. of ethanol is produced. 2,4-Dinitrophenol acts like azide, but requires a much higher concn. for 50% inhibition. Salicylaldoxime and Na diethyldithiocarbamate also act like azide, but are even less effective than 2,4-dinitrophenol. Monoiodoacetate (0.005 [image]) entirely inhibits acid and ethanol production, whereas fluoroacetate has no appreciable effect. The facts of the acid secretion are well explained by a redox theory, in which it is considered that the H+ ions are produced in an outer cell region by the ionization of the reduced form of a heavy metal catalyst, receiving metabolic H atoms from a dehydrogenase (directly or at one or more removes) and being in turn oxidized within the cell where it receives H+ ions and transfers H atoms to an acceptor. This redox theory has an obvious application to secretion of acid by the gastric mucosa, the facts of acid secretion by yeast being now strikingly similar to acid secretion by the parietal cells. Other applications may also be entertained, such as acidification in the nephrons of the kidney or alkalinization by the pancreas.
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