Regulation of pyrimidine nucleotide formation in Pseudomonas reptilivora

AIMS: To study the regulation of de novo pyrimidine biosynthesis in the pathogenic bacterium Pseudomonas reptilivora ATCC 14836. METHODS AND RESULTS: The pyrimidine biosynthetic pathway enzymes were assayed in extracts of Ps. reptilivora ATCC 14836 cells and of cells from an auxotroph lacking aspartate transcarbamoylase activity. Pyrimidine biosynthetic pathway enzyme activities in ATCC 14836 were influenced by the addition of pyrimidine bases to the culture medium with orotic acid addition inducing dihydroorotase activity. Pyrimidine starvation of the transcarbamoylase mutant strain increased its de novo enzyme activities suggesting that the de novo pathway was also subject to repression by a pyrimidine-related compound. Aspartate transcarbamoylase activity in ATCC 14836 was inhibited in vitro by pyrophosphate and ATP. CONCLUSIONS: Regulation of pyrimidine biosynthesis in Ps. reptilivora was observed at the level of enzyme synthesis and at the level of activity for aspartate transcarbamoylase. Its regulation of enzyme synthesis seemed to be more highly controlled than what was observed in the related species Ps. fluorescens. SIGNIFICANCE AND IMPACT OF THE STUDY: This investigation found that pyrimidine biosynthesis is controlled in Ps. reptilivora. This could prove helpful to future studies exploring its pathogenicity.