Molecular and General Genetics MGG

, Volume 148, Issue 1, pp 49–55

Multiple regulation of nucleoside catabolizing enzymes in Escherichia coli: Effects of 3:5′ cyclic AMP and CRP protein

  • Karin Hammer-Jespersen
  • Per Nygaard
Article

Summary

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.

Enzymes

Purine nucleoside phosphorylase or purine nucleoside: orthophosphate (deoxy) ribosyltransferase (EC 2.4.2.1) thymidine phosphorylase or thymidine: orthophosphate deoxyribosyltransferase (EC 2.4.2.4) uridine phosphorylase or uridine: orthophosphate ribosyltransferase (EC 2.4.2.3) cytidine deaminase or (deoxy) cytidine aminohydrolase (EC 3.5.4.5) deoxyriboaldolase or 2-deoxy-D-ribose-5-phosphate acetaldehydelase (EC 4.1.2.4) phosphodeoxyribomutase (EC 2.7.5.6) 

Abbreviations and Symbols

cAMP

cyclic adenosine 3:5′-monophosphate

CRP

cAMP receptor protein. Genes coding for: adenyl cyclase

cya

cAMP receptor protein

crp

cytidine deaminase

cdd

uridine phosphorylase

udp

thymidine phosphorylase

tpp

purine nucleoside phosphorylase

pup; cytR

regulatory gene for cdd, udp, dra, tpp, drm, and pup

deoR

regulatory gene for dra, tpp, drm, and pup

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References

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Copyright information

© Springer-Verlag 1976

Authors and Affiliations

  • Karin Hammer-Jespersen
    • 1
  • Per Nygaard
    • 1
  1. 1.University Institute of Biological Chemistry BCopenhagenDenmark

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