Rates of synthesis of cyclic 3',5'-adenosine monophosphate (cAMP) were measured in cultures of Escherichia coli aerating without a carbon source. This technique provides a representative measure of adenylate cyclase activity in the absence of inhibition caused by transport of the carbon source. Aden
Multiple regulation of nucleoside catabolizing enzymes in Escherichia coli: Effects of 3:5′ cyclic AMP and CRP protein
✍ Scribed by Hammer-Jespersen, Karin ;Nygaard, Per
- Publisher
- Springer
- Year
- 1976
- Tongue
- English
- Weight
- 607 KB
- Volume
- 148
- Category
- Article
- ISSN
- 0026-8925
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✦ Synopsis
The regulation of the synthesis of nucleoside metabolizing enzymes has been studied in cya and crp mutant strains of Escherichia coli. The synthesis of the cyt-enzymes, cytidine deaminase and uridine phosphorylase regulated by the cytR gene product, is activated by the cAMP-CRP complex. On the other hand the synthesis of the deoenzymes: deoxyriboaldolase, thymidine phosphorylase, phosphodeoxyribomutase and purine nucleoside phosphorylase, appears to be increased if an active cAMP-CRP complex cannot be formed. It also seems that nucleosides serve as poor carbon sources for cya and crp mutants; this could not solely be explained by low levels of nucleoside metabolizing enzymes nor by a deficiency in nucleoside uptake. Addition of casamino acids stimulated the growth of cya and crp mutants, with nucleosides as carbon sources. When grown on glucose and casamino acids growth could be stimulated by adenine and hypoxanthine nucleosides; these results suggest an impaired nitrogen metabolism in cya and crp mutants.
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