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Regulation of pyrimidine formation in Pseudomonas lundensis

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The regulation of pyrimidine formation in the food spoilage agent Pseudomonas lundensis ATCC 49968 by pyrimidines was examined. In P. lundensis cells grown on glucose as a carbon source, the enzymes aspartate transcarbamoylase, dihydroorotase, and orotidine 5′-monophosphate decarboxylase were induced by orotic acid. Pyrimidine auxotrophs containing reduced transcarbamoylase or orotate phosphoribosyltransferase activity were isolated using chemical mutagenesis and selection procedures. Independent of carbon source, the maximum derepression of enzyme activity was observed for orotidine 5′-monophosphate decarboxylase after pyrimidine limitation of either auxotroph. In the glucose-grown cells of the transcarbamoylase mutant strain, orotic acid induced dihydroorotase and decarboxylase activities. Aspartate transcarbamoylase activity in succinate-grown P. lundensis cells was highly regulated by pyrophosphate as well as by pyrimidine and purine ribonucleotides. It was concluded that pyrimidine formation in P. lundensis was controlled both at the level of de novo pyrimidine biosynthetic enzyme synthesis and at the level of transcarbamoylase activity.

L’autorégulation de la formation des pyrimidines chez Pseudomonas lundensis ATCC 49968, un agent de contamination des aliments, a été examinée. Chez P. lundensis cultivée sur du glucose utilisé comme source de carbone, l’aspartate transcarbamoylase, la dihydrooratase et l’OMP décarboxylase étaient induites par l’acide orotique. Des bactéries auxotrophes aux pyrimidines dont l’activité transcarbamoylase et orotate phosphoribosyltransférase était réduite ont été générées par mutagenèse chimique et isolées par des protocoles de sélection. Indépendamment de la source de carbone, une dérépression maximale de l’activité enzymatique a été observée avec l’OMP décarboxylase suite à une limitation en pyrimidine chez tous les auxotrophes. L’acide orotique induisait une activité dihydroorotase et décarboxylase chez les cellules cultivées en présence de glucose et provenant de la souche dont la transcarbamoylase était mutée. L’activité de l’aspartate transcarbamoylase de P. lundensis cultivée sur du succinate était hautement réglée par le pyrophosphate, ainsi que par les ribonucléotides de pyrimidines et de purines. Nous concluons que la formation de pyrimidines chez P. lundensis est contrôlée tant au niveau de la synthèse de novo des enzymes de biosynthèse des pyrimidines qu’au niveau de l’activité transcarbamoylase.

Document Type: Research Article

Publication date: 2009-03-01

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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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