The action of some detergents on succinate dehydrogenase of E. coli was investigated in vivo. The enzyme activity was activated by sodium cholate (SC), glycerol monocaprate (MC10), Brij 58 and Triton X-100 but inhibited by Tween 20, sodium lauroyl sarcosinate and sodium dodecyl sulfate. In sodium deoxycholate (DOC), the enzyme activity was slightly activated in the presence of 0.2% DOC but not activated in 1.0% DOC. The enzyme activity was also activated by pretreating the cells with SC, DOC or MC10. On the contrary, the enzyme activity of the cell envelope prepared from the cells was strongly inhibited by these detergents. The enzyme activity of the cells cultured in detergent medium containing SC, DOC or MC10 was higher than that of the normal cells. The enzyme activity was the highest in the cells cultured at 20℃, followed by the cells cultured at 30℃ and then at 40℃ in order of decreasing activity. However, the activation of the enzyme by SC or MC10 was higher in the cells cultured at high temperature than those cultured at low temperature. On the other hand , the enzyme activity of the cells cultured at 20℃ was inhibited by DOC but was activated in case of the cells cultured at 40℃. The enzyme activity was inhibited by cross-linking the outer membrane with dimethylsuberimidate; besides, the enzyme activity of the cells cross-linked was markedly inhibited by detergents. These results suggest that these detergents do not directly act on the enzyme of the cells, but rather on the outer membrane-peptidoglycan layer and the permeability of the layer would alter as a result of the action. The variation of enzyme activity, in vivo, may be dependent on the permeability of the altered layer to the substrates.
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