清酒酵母の生理的研究 : (第15報)乳酸による菌体内酵素の不活性化について

概要

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When cells of Saccharomyces sake were soaked in various concentrations of lactic acid solutions, incorporation of the acid into the cells occurred to various degrees mainly upon the acid concentration and also to a lesser extent upon the soakage temperature. The acid taken into the cells resulted in lowering the intracellular pH; for example, the pH of cell-free extracts obtained from normal cells was about 6.3,whereas that of cells soaked in 0.2 N lactic acid at 30℃ lowered to ca. 4. The presence of glucose in the soakage moderated the lowering of the intracellular pH. The soakage also caused marked decreases in the activieties of intracellular enzymes, such as hexokinase, pyruvate decarboxylase and D-lactate dehydrogenase. In vitro experiments showed that hexokinase, one of the typical enzymes in glycolytic pathway, was seriously inactivated when allowed to stand at pH 4 at 30℃ for few hours and that an addition of glucose to the solution prevented the enzyme inactivation significantly.These results suggest a possible explanation about the lethal action of lactic acid on Saccharomyces sake under anaerobic conditions and the protecting effect of glucose on these enzymes as mentioned in our previous papers.
社団法人日本生物工学会の論文
1971-04-25