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Pyrimidine nucleotide synthesis in Pseudomonas citronellolis

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Pyrimidine biosynthesis was active in Pseudomonas citronellolis ATCC 13674 and appeared to be regulated by pyrimidines. When wild-type cells were grown on succinate in the presence of uracil, the de novo enzyme activities were depressed while only four enzyme activities were depressed in the glucose-grown cells. On either carbon source, orotic acid-grown cells had diminished aspartate transcarbamoylase, dihydroorotase or OMP decarboxylase activity. Pyrimidine limitation of glucose-grown pyrimidine auxotrophic cells resulted in de novo enzyme activities, except for transcarbamoyolase activity, that were elevated by more than 5-fold compared to their activities in uracil-grown cells. Since pyrimidine limitation of succinate-grown mutant cells produced less enzyme derepression, catabolite repression appeared to be a factor. At the level of enzyme activity, aspartate transcarbamoylase activity in P. citronellolis was strongly inhibited by all effectors tested. Compared to the regulation of pyrimidine biosynthesis in taxonomically-related species, pyrimidine biosynthesis in P. citronellolis appeared more highly regulated.Key words: pyrimidine biosynthesis, regulation, Pseudomonas citronellolis, auxotroph, aspartate transcarbamoylase, inhibition.

La biosynthèse des pyrimidines était active chez Pseudomonas citronellolis ATCC 13674 et semblait être régulée par les pyrimidines. Lorsque les cellules de type sauvage furent cultivées sur du succinate en présence d'uracile, les activités enzymatiques de la voie de novo ont été réprimées tandis que seulement quatre activités enzymatiques furent réprimées chez les cellules cultivées en présence de glucose. Sur les deux sources de carbone, les cellules cultivées en présence d'acide orotique ont démontré de plus basses activités d'aspartate transcarbamoylase, de dihydroorotase ou d'OMP décarboxylase. La restriction en pyrimidines chez des cellules auxotrophes pour les pyrimidines et cultivées sur du glucose a induit les activités enzymatiques de novo, sauf pour l'activité transcarbamoylase, qui étaient plus de 5 fois supérieures à celles mesurées chez les cellules cultivées sur de l'uracile. Puisque la restriction en pyrimidines chez des cellules mutantes cultivées sur du succinate a entraîné une dérépression enzymatique moins intense, la répression catabolique semble être un facteur. Au niveau des activités enzymatiques, l'activité aspartate transcarbamoylase chez P. citronellolis a été fortement inhibée par tous les effecteurs analysés. Comparativement à la régulation de la biosynthèse des pyrimidines chez des espèces apparentées taxonomiquement, la biosynthèse des pyrimidines semble davantage régulée chez P. citronellolis.Mots clés : biosynthèse des pyrimidines, régulation, Pseudomonas citronellolis, auxotrophe, aspartate transcarbamoylase, inhibition.[Traduit par la Rédaction]

Document Type: Research Article

Publication date: 2004-06-01

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  • Published since 1954, this monthly journal contains new research in the field of microbiology including applied microbiology and biotechnology; microbial structure and function; fungi and other eucaryotic protists; infection and immunity; microbial ecology; physiology, metabolism and enzymology; and virology, genetics, and molecular biology. It also publishes review articles and notes on an occasional basis, contributed by recognized scientists worldwide.
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