Release of Nitrogenous Substances by Brewer's Yeast IV. Energetics in Shock Excretion of Amino Acids

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Lewis, M. J. (University of California, Davis), and H. J. Phaff. Release of nitrogenous substances by brewer's yeast. IV. Energetics in shock excretion of amino acids. J. Bacteriol. 89:960–966. 1965.—When suitably grown yeast cells are suspended in a solution of fermentable sugar, amino acids from the internal pool are rapidly released from the cells, a phenomenon referred to as shock excretion. After approximately 2 to 3 hr, in the presence of excess sugar, the amino acids are almost completely reabsorbed. This observation has been further studied with particular reference to the energy-yielding reactions of the cell. It has been established that amino acid release increases more rapidly with a rise in incubation temperature than does fermentation rate. Amino acid release cannot be inhibited by the common uncouplers of adenosine triphosphate synthesis (azide, arsenate, or 2,4-dinitrophenol) at concentrations adequate to prevent reabsorption of amino acids—an energy-requiring event. Inhibitors which completely inhibit the dissimilation of glucose (such as iodoacetate and fluoride) or those preventing entry of glucose into the cell (uranyl acetate) are effective in preventing amino acid release. It was concluded that shock excretion of amino acids is independent of energy-yielding reactions, but may be the result of changes in the state of the cell contingent upon the continuous flow of a fermentable sugar across the cell membrane.

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