Document Type

Thesis - University Access Only

Award Date


Degree Name

Master of Science (MS)

Department / School



Regulation of pyrimidine biosynthesis at the level of gene expression and enzyme activity was investigated in Pseudomonas oleovorans ATCC 8062. Growth of P. oleovorans cells on exogenous uracil induced aspartate transcarbamoylase and dihydroorotase activities but repressed the activities of dihydroorotate dehydrogenase, orotate phosphoribosyltransferase and OMP decarboxylase. It was concluded that aspartate transcarbamoylase and dihydroorotase activities were both inducible since protein synthesis was required to increase their activities after the introduction of uracil into the growth medium. The pyrimidine starvation experiments involving two uracil auxotrophic mutant strains, isolated in this study by a combination of chemical mutagenesis and antibiotic counterselection, also indicated repression of de nova pyrimidine biosynthetic pathway enzyme synthesis. After starving these two strains for pyrimidines, the activities of the de nova enzymes were found to increase after pyrimidine limitation for two or four hours. At the level of enzyme activity, regulation of the P. oleovorans aspartate transcarbamoylase activity was shown to be highly regulated. Under saturating substrate conditions, UTP, UDP, ATP, and pyrophosphate were most inhibitory of enzyme activity. Overall, the findings of this study indicate that de nova pyrimidine biosynthesis is highly regulated in P. oleovorans ATCC 8062.

Library of Congress Subject Headings

Pyrimidines -- Synthesis



Number of Pages



South Dakota State University