Role of materials released from Escherichia coli cells in the catabolite repression of L- arabinose isomerase induced by γ-irradiation

Abstract

Inhibition of L-arabinose isomerase synthesizing capacity of Escherichia coli by γ-irradiation was withdrawn when the irradiated cells were separated by centrifugation from the suspending medium and were suspended in a fresh growth medium. Further, there was an inhibition of the induced enzyme synthesis in unirradiated cells when suspended in the supernatant from γ-irradiated cell suspension. These findings suggested that some inhibitory materials) was released from γ-irradiated cells into the suspending medium. Incubation of γ-irradiated cells suspended in fresh growth medium led to an exponential decrease in the enzyme synthesizing capacity, which was not caufyed by release of any inhibitory material Cyclic AMP could reverse the inhibition of the enzyme synthesizing capacity in unirradiuted cells caused by their suspension in the supernatant from γ-irradiated cell suspension immediately following irradiation suggesting that catftbolite repression is the cause of the inhibition. Incubation of γ-irradiated cell suspension released the L arabinose isomerave-syntriesizing system from the catabolite repression.