ENZYMATIC ACTIVITIES OF STREPTOMYCIN-DEPENDENT ESCHERICHIA COLI IN RELATION TO VALINE FORMATION

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Bragg, P. D. (University of British Columbia, Vancouver, B.C., Canada), and W. J. Polglase. Enzymatic activities of streptomycin-dependent Escherichia coli in relation to valine formation. J. Bacteriol. 88:1399–1402. 1964.—The activities of several enzymes were compared in antibiotic-depleted and antibiotic-supplemented streptomycin-dependent Escherichia coli. Depleted cells were somewhat lower than supplemented cells in several oxidase activities. Isocitric dehydrogenase was very much lower in depleted cells than in supplemented cells. The lactic dehydrogenase activity of depleted and supplemented cells was similar. The balance of enzymatic activities in depleted and supplemented cells was thus found to correlate well with the observed extracellular products. Thus, depleted cells excreted lactic acid and were deficient in oxidase activity (although normal in lactic dehydrogenase activity), whereas supplemented cells excreted valine and were rich in the reduced nicotinamide adenine dinucleotide phosphate-producing enzyme, isocitric dehydrogenase. Since antibiotic-depleted cells were not deficient in lactic dehydrogenase, it appeared probable that the failure of depleted cells to metabolize lactate was related to a deficiency in the electron-transport system.

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