Regulation of Pyrimidine Ribonucleoside Salvage Metabolism in Pseudomonas putida ATCC 17536

Pyrimidine base and ribonucleoside salvage metabolism was investigated in Pseudomonas putida ATCC 17536 cells. In ATCC 17536 cell extracts, the pyrimidine ribonucleoside salvage enzymes nucleoside hydrolase and cytosine deaminase activities were measurable while uridine phosphorylase activity was not. Carbon and nitrogen sources influenced the levels of the salvage pathway enzyme activities in P. putida ATCC 17536. Catabolite repression by a glucose metabolite of nucleoside hydrolase and cytosine deaminase synthesis in ATCC 17536 cells compared to cells grown on the carbon source succinate or ribose was observed while a nitrogen metabolite appeared to be controlling pyrimidine salvage enzyme synthesis. When glucose was the carbon source, ATCC 17536 cells grown on uracil or 5-methylcytosine as a nitrogen source caused at least a 5-fold increase in hydrolase and deaminase synthesis relative to their activities in ammonium sulfate-grown cells. In succinate-grown ATCC 17536 cells, thymine or 5-methylcytosine as a nitrogen catabolite produced at least double the hydrolase or deaminase activity relative to either activity in ammonium sulfate-grown cells. Overall, the pyrimidine base and ribonucleoside salvage enzymes in P. putida ATCC 17536 biovar B cells were regulated by the carbon or nitrogen source with pyrimidine salvage metabolism differing in biovar A and B strains.