Sequential Synthesis of Histidine-degrading Enzymes in Bacillus subtilis

Abstract l-Histidine induces the formation of the four enzymes constituting the histidine-degrading pathway in Bacillus subtilis. Studies of the kinetics of induction of histidase and of FGA hydrolase demonstrated that the two enzymes appear after induction in sequence, separated by a 2-min interval. The results of experiments in which chloramphenicol was used to arrest peptide bond formation indicate that both enzymes are first formed as enzymatically inactive precursors. The basis for the sequential appearance of these enzymes and of their precursors was shown to be the sequential appearance of their respective enzyme-forming capacities. Experiments using rifampicin, an inhibitor of the initiation of transcription, provide good evidence that the synthesis of messenger RNA specifying both enzymes is initiated upon addition of the inducer. These findings support the hypothesis that the structural genes of the two enzymes are transcribed into a single polycistronic messenger.