ISSN:
1573-4919
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Chemistry and Pharmacology
,
Medicine
Notes:
Summary The synergistic effects of potential amino donors were studied in the assay of CTP synthetase in extracts of Chinese hamster fibroblasts. We found that L-glutamine was not effective as the sole amino donor, but combinations of L-glutamine with NH4HCO3, L-arginine or potassium phosphate did result in the conversion of UTP to CTP. L-arginine or potassium phosphate were also not effective when used alone, and NH4HCO3 was only slightly effective. Our studies demonstrate that the individual synergistic combinations were not additive; multiple combinations of components decreased rather than increased the formation of CTP. The synergistic combinations of L-glutamine with either NH4HCO3 or L-arginine had an absolute requirement for ATP; when ATP and PEP were absent no conversion of UTP to CTP occurred. The presence of GTP in a reaction mixture slightly increased the formation of CTP when L-glutamine and NH4HCO3 were used and substantially increased CTP formation when L-glutamine and L-arginine were used.De novo CTP synthesis was greatly reduced when nonradioactive CTP was added to an assay mixture, suggesting feedback inhibition. A TLC procedure has been developed that allows for the direct separation of UTP and CTP without requiring prior conversion to the mononucleotide or nucleoside level.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00849193
