Regulation of Pyrimidine Biosynthesis in Pseudomonas Monteilii

Document Type


Degree Name

Master of Science (MS)



Date of Award

Summer 2017


The regulation of the de novo pyrimidine biosynthetic pathway in Pseudomonas monteilii ATCC 700476 by pyrimidines was studied. The pathway enzyme activities were higher in succinate grown cells than that of glucose grown cells. Catabolite repression of the pathway enzyme activities seemed to be evident following cell growth on glucose as a carbon source. When glucose was used as the carbon source, orotate phosphoribosyltransferase and orotidine 5’-monophosphate decarboxylase activities were significantly decreased by uracil supplementation. When succinate was used as the carbon source, aspartate transcarbamoylase activity was significantly decreased in presence of uracil or orotic acid. Pyrimidine auxotrophic mutants were successfully isolated by two different methods. One mutant exhibited depressed orotate phosphoribosyltransferase activity while the other lacked dihydroorotase activity. Although both mutant strains had their pyrimidine requirement met by uracil or cytosine, the dihydroorotase mutant could also utilize orotic acid if glucose served as the carbon source. After pyrimidine limitation of both auxotrophic mutant strains, the phosphoribosyltransferase mutant strain JW-1 exhibited the highest derepression of the four active pyrimidine biosynthetic enzyme activities independent of carbon source. Pyrimidine limitation of the dihydroorotase mutant strain JW-2 showed a lesser degree of derepression. It did appear that orotidine 5’- monophosphate or uridine 5’- monophosphate may have served as a co-repressing metabolite interacting with a repressor protein to halt pyrimidine pathway enzyme synthesis. At the level of enzyme activity, aspartate transcarbamoylase in P. monteilii was strongly regulated by CTP, ADP, GMP and UMP.


Thomas P. West

Subject Categories

Chemistry | Physical Sciences and Mathematics