Influence of carbon source on pyrimidine synthesis in Pseudomonas mendocina.

The effect of carbon source on the regulation of the de novo pyrimidine biosynthetic enzymes in the bacterium Pseudomonas mendocina was studied. When glucose was the carbon source, orotic acid supplementation of P. mendocina cells produced the greatest depression of aspartate transcarbamoylase, dihydroorotate dehydrogenase and orotate phosphoribosyltransferase activities while P. mendocina cells grown in the presence of uracil caused the maximal decrease in dihydroorotase and OMP decarboxylase activities. After the pyrimidine starvation of an orotate phosphoribosyltransferase mutant strain of P. mendocina grown on glucose, the pyrimidine biosynthetic pathway enzyme activities were generally diminished. With respect to pyrimidine starvation studies, the carbon source glucose appeared to lessen regulation at the level of enzyme synthesis compared to what has been observed when succinate served as the carbon source. The regulation of the pyrimidine biosynthetic pathway by carbon source in P. mendocina appeared to differ from how carbon source influenced the control of pyrimidine biosynthesis in the closely-related species Pseudomonas stutzeri.