Resistance to Catabolite Repression of Histidase and Proline Oxidase during Nitrogen-limited Growth of Klebsiella aerogenes

Abstract In Klebsiella aerogenes β-galactosidase and histidase are subject to strong catabolite repression by glucose in the presence of a good source of nitrogen. Under conditions of nitrogen limitation, the catabolite repression of histidase is relieved, while β-galactosidase remains strongly repressed. Exogenous adenosine 3',5'-monophosphate relieves the catabolite repression of both histidase and β-galactosidase. A mutant which requires exogenous adenosine 3',5'-monophosphate for the synthesis of many catabolite-sensitive enzymes is able to utilize histidine and synthesize histidase at a rapid rate under conditions of nitrogen limitation in the absence of adenosine 3',5'-monophosphate. Proline oxidase, like histidase, is subject to catabolite repression and is synthesized rapidly in the presence of glucose when the supply of nitrogen is limited. The adenosine 3',5'-monophosphate requiring mutant is able to utilize proline as a sole nitrogen source in the presence of glucose without exogenous adenosine 3',5'-monophosphate. In Salmonella typhimurium, histidase is strongly repressed by glucose, even in nitrogen-starved cells. When histidase genes from S. typhimurium were transferred on an episome to cells of K. aerogenes carrying a deletion of the histidase gene, catabolite repression of histidase was relieved by nitrogen limitation. It is concluded that in K. aerogenes certain catabolitesensitive enzymes which degrade nitrogenous compounds are synthesized rapidly in the presence of glucose if the supply of nitrogen is limited. This rapid synthesis is mediated by a cytoplasmic factor which acts independently of adenosine 3',5'-monophosphate.