Royal Society Publishing

Studies of the Enzyme Activity of Bact. lactis aerogenes (Aerobacter aerogenes). II. The Effects of Various Adaptations on the Enzyme Balance

D. J. W. Grant , Cyril Hinshelwood


A study has been made of the changes in enzyme balance accompanying the adaptation of Bact. lactis aerogenes to resist various drugs or to utilize lactose. Enzymes directly responsible for the breakdown of the source of carbon and energy prove, in general, to be expanded in cells resistant to streptomycin or crystal violet. Training to these drugs appears to transfer metabolism to anaerobic routes requiring more of the carbon source and thus needing a greater activity of the degradative enzymes. Training to both drugs jointly, however, leaves these enzyme activities unchanged or actually reduces them. After adaptation to resist proflavine, the oxidative and catabolic processes are less active than before, whereas asparagine deaminase, representing part of the amino-acid metabolism, is expanded, perhaps in compensation. The activities of enzymes normally latent in the cell and capable of degrading carbon sources which the cell has not previously used are usually, but not invariably decreased by drug training. In the development of a new cellular economy these enzymes may apparently have to be partially sacrificed. Training to chloramphenicol does not alter the activities of the enzymes studied. Catalase shows little change during training to most of the drugs. During adaptation to utilize lactose the activity of every enzyme studied changes in a way which suggests a co-ordinated pattern. Those enzymes responsible for the breakdown of lactose are expanded and the activities of the non-induced enzymes all show a complex pattern linked with this. Catalase activity falls but asparagine deaminase activity rises.

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