Consequences of Lysine Oversynthesis in Pseudomonas Mutants Insensitive to Feedback Inhibition

Regulation of lysine biosynthesis was studied in Pseudomonas putida and Pseudomonas acidovorans. In both species, aspartokinase was subject to feedback inhibition by lysine and threonine and dihydrodipicolinate synthetase was inhibited by lysine. P. acidovorans could not degrade lysine whereas P. putida degraded lysine through an inducible lysine oxygenase. P. putida mutants with an aspartokinase insensitive to lysine inhibition were obtained. They did not excrete lysine but their lysine oxygenase was endogenously induced. However mutants obtained from a mutant lacking lysine oxygenase still did not excrete lysine. P. acidovorans mutants with a dihydrodipicolinate synthetase desensitized towards lysine inhibition were obtained. From them double mutants with both dihydrodipicolinate synthetase and aspartokinase desensitized were also obtained. All of these mutants excreted lysine.