The Origin of the Reaction of Harden and Young in Cell-free Alcoholic Fermentation*

Since adenosine triphosphate (ATP)l transfers its labile phosphate to glucose, for every mole of triose phosphate oxidized 1 mole of inorganic phosphate is taken up by the fermenting system. Besides this uptake, an internal cycle exists for the second phosphate group, which is already present in the triose phosphate and after oxidation appears finally in the phosphopyruvic acid. This phosphate is also transferred to glucose or hexose monophosphate and reappears therefore in a new molecule of triose phosphate. This internal cycle does not add new phosphate to the system in the stationary state and can therefore be omitted from the discussion. However, another aspect of the reaction of Harden and Young is less obvious. In cell-free fermentation two phases follow each other. First there is a rapid phase, “phosphate period,” for which equation (1) applies;