Abstract
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.
Highlights
We found that the control of histidase is essentially the same as that reported by Neidhardt and Magasanik for K. aerogenes strain 1033
All strains are derived from K. aerogenes strain W-70, except for strains with the prefix NE which are derivatives of S. lyphimurium strain 15-59. gal, inability to utilize galactose; hu& illability to utilize histidine; huts, hut genes derived from 8. typhimurium; bio, requirement for biotin; ch,Z, resistance to chlorate; hut C, constitutive synthesis of histidine-degrading enzymes; pur, requirement for purine; thy/l, requirement for thymine; thyR, ability to utilize thymine at low levels (4pg per ml) ; (F’), carrying an F factor containing the indicated bacterial genes. hut*511 is an abbreviated designation for the K. aerogenes deletion gal-chlhut-bio-511; hut*162 is an abbreviated designation for t,hc S
NK-53, which is constitutive for the synthesis of the histidine-degrading enzymes, was grown on several media containing n-proline. ds shown in Table IV, proline oxidase was repressed approximately 3-fold when the cells were growli on a mixture of glucose, ammonium sulfate, and proline as compared with those growing on a mixture of citrate, ammonium sulfate, and proline
Summary
In Klebsiella aerogenes P-galactosidase and histidase are subject to strong catabolite repression by glucose in the presence of a good source of nitrogen. 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. Neidhnrdt and h’lagasanik [5] observed strong catabolite repression of histidase by glucose when K. aerogenes was grown on medium containing glucose, histidine, and ammonium sulfate They found little catabolite repression when the cells were grown on glucose with histidine as the only nitrogen source. If glucose could repress histidase under these conditions, the cells would not be able to utilize the histidine in the medium as a source of nitrogen, and, would not grow. Cylic AMP3 relieves catabolite repression of P-gnlactosidase, whereas nitrogen limitation increases catabolite repression of this enzyme
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