Regulation of Purine and Pyrimidine Metabolism

Gots, Joseph S.

doi:10.1016/b978-0-12-299255-1.50015-8

Cited by 22 publications

(17 citation statements)

References 178 publications

(88 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Once cellular levels of purine nucleotides have been attained, further nucleotide loading will inhibit adenine-PRTase and hypoxanthine-guanine PRTase activities (Murray, 1971). Regulation of enzymatic activities also influences the cellular uptake of salvage substrates due to their uptake being proportional to PRTase activities (Gots, 1971). Once cellular purine nucleotide requirements are met, surplus nucleosides and free bases are diverted towards catabolic pathways leading to the formation of purine metabolites.…”

Section: De Novo Synthesismentioning

confidence: 99%

“…De novo purine synthesis has been extensively reviewed in the literature (refer to Hartman, 1970;Gots, 1971;Henderson and Patterson, 1973) and is only briefly documented. Tissue de novo purine synthesis proceeds using 5'-phosphoribosyl-1 '-pyrophosphate (PRPP) as a building block onto which glycine, glutamine, aspartate, one carbon unit and carbon dioxide precursors are incorporated to yield a purine ring (Lehninger, 1982).…”

Section: De-novo Synthesismentioning

confidence: 99%

“…Xanthine may be salvaged by hypoxanthine-guanine PRTase to form xanthine monophosphate (Gots, 1971), but this reaction is very slow due to a low affinity of xanthine for this enzyme (Hitchings, 1978). Purine bases can also be salvaged by combining with ribose l'-phosphate to yield their respective nucleosides.…”

Section: Salvage Pathwaysmentioning

confidence: 99%

See 2 more Smart Citations

Estimation of microbial protein supply in ruminant animals based on renal and mammary purine metabolite excretion. A review

Shingfield¹

2000

J. Anim. Feed Sci.

View full text Add to dashboard Cite

The potential of mammary and renal purine metabolite excretion as a technique for the assessment of microbial protein supply in ruminant animals is reviewed. Data reported in the literature tends to support the validity of the assumptions of the technique that purines entering the duodenum are essentially microbial in origin and that following metabolism, purine catabolites (collectively allantoin, hypoxanthine, uric acid and xanthine) are quantitatively recovered in urine. The most convincing experimental evidence suggests that secretion of purine metabolites in milk is of little value for the assessment of microbial protein supply due a mumal correlation with milk yield. In contrast, use of urinary purine metabolite excretion does appear to provide estimates of microbial protein supply that, are in general, consistent with values derived using standard in vivo procedures. However, the accuracy of this approach is largely dependent on obtaining representative samples of rumen microbes and the ability to account for variations in non-renal excretion and endogenous purine losses. In conclusion, urinary purine metabolite excretion appears to represent a valid noninvasive procedure to assess relative differences, rather than quantitative estimates of microbial protein supply in ruminant animals.

show abstract

Section: De Novo Synthesismentioning

confidence: 99%

Section: De-novo Synthesismentioning

confidence: 99%

See 1 more Smart Citation

Estimation of microbial protein supply in ruminant animals based on renal and mammary purine metabolite excretion. A review

Shingfield¹

2000

J. Anim. Feed Sci.

View full text Add to dashboard Cite

show abstract

“…This will be discussed in relation to nucleic acid synthesis. Several reviews on this subject have dealt with microbial and animal systems (GOTS 1970, MURRAY 1971, MURRAY et al 1970, O'DONNOVAN and NEUHARD 1970, HARTMAN 1970, HENDERSON 1972, HENDER-SON and PATERSON 1973. However, purine and pyrimidine metabolism in plants has not been discussed in detail before.…”

Section: Introductionmentioning

confidence: 99%

Metabolism of Pyrimidines and Purines

Wasternack¹

1982

Nucleic Acids and Proteins in Plants II

View full text Add to dashboard Cite

“…De novo synthesis of purine nucleotides requires a minimum of 10 enzymes for the production of IMP, the major intermediate of purine metabolism (6). The salvage of nucleobases and nucleosides provides an energy-saving alternative.…”

mentioning

confidence: 99%

Characterization of guanine and hypoxanthine phosphoribosyltransferases in Methanococcus voltae

1996

View full text Add to dashboard Cite

Phosphoribosyltransferase (PRTase) and nucleoside phosphorylase (NPase) activities were detected by radiometric methods in extracts of Methanococcus voltae. Guanine PRTase activity was present at 2.7 nmol min ؊1 mg of protein ؊1 and had an apparent K m for guanine of 0.2 mM and a pH optimum of 9. The activity was inhibited 50% by 0.3 mM GMP. IMP and AMP were not inhibitory at concentrations up to 0.6 mM. Hypoxanthine inhibited by 50% at 0.16 mM, and adenine and xanthine were not inhibitory at concentrations up to 0.5 mM. Guanosine NPase activity was present at 0.01 nmol min ؊1 mg of protein ؊1. Hypoxanthine PRTase activity was present at 0.85 nmol min ؊1 mg of protein ؊1 with an apparent K m for hypoxanthine of 0.015 mM and a pH optimum of 9. Activity was stimulated at least twofold by 0.05 mM GMP and 0.2 mM IMP but was unaffected by AMP. Guanine inhibited by 50% at 0.06 mM, but adenine and xanthine were not inhibitory. Inosine NPase activity was present at 0.04 nmol min ؊1 mg of protein ؊1. PRTase activities were not sensitive to any base analogs examined, with the exception of 8-azaguanine, 8-azahypoxanthine, and 2-thioxanthine. Fractionation of cell extracts by ion-exchange chromatography resolved three peaks of activity, each of which contained both guanine and hypoxanthine PRTase activities. The specific activities of the PRTases were not affected by growth in medium containing the nucleobases. Mutants of M. voltae resistant to base analogs lacked PRTase activity. Two mutants resistant to both 8-azaguanine and 8-azahypoxanthine lacked activity for both guanine and hypoxanthine PRTase. These results suggest that analog resistance was acquired by the loss of PRTase activity.De novo synthesis of purine nucleotides requires a minimum of 10 enzymes for the production of IMP, the major intermediate of purine metabolism (6). The salvage of nucleobases and nucleosides provides an energy-saving alternative. Salvage pathways have been identified in eubacteria, eucaryotes, and archaebacteria and comprise a collection of enzymes capable of converting preformed nucleobases and nucleosides to AMP, GMP, IMP, and XMP (5,7,10,13,17,19,21,23,29). These enzymes enable organisms to use exogenous bases liberated from lysed cells or recycle those produced by the breakdown of unstable RNA. A key enzyme in the pathway is phosphoribosyltransferase (PRTase). This enzyme is responsible for the conversion of bases to nucleotide 5Ј-monophosphates by use of 5-phosphorylribose-1-pyrophosphate (PPRP) as the phosphopentose donor. Bases can also be salvaged by nucleoside phosphorylases by use of ribose-1-phosphate as the phosphopentose donor. However, in Escherichia coli and Salmonella typhimurium, this mechanism is a minor source of nucleotides (20).Mutants resistant to nucleobase analogs have been isolated from several archaebacteria (2,12,16,29). As with eubacteria and eucaryotes, these mutants have lost the ability to incorporate certain exogenous bases, and this loss is almost always accompanied by a loss of the corresponding PRTase ac...

show abstract

Regulation of Purine and Pyrimidine Metabolism

Cited by 22 publications

References 178 publications

Estimation of microbial protein supply in ruminant animals based on renal and mammary purine metabolite excretion. A review

Estimation of microbial protein supply in ruminant animals based on renal and mammary purine metabolite excretion. A review

Metabolism of Pyrimidines and Purines

Characterization of guanine and hypoxanthine phosphoribosyltransferases in Methanococcus voltae

Contact Info

Product

Resources

About