The Role of Anaplerotic Reactions for Oxaloacetate Synthesis in the L-Lysine-Producing Strain of Corynebacterium glutamicum
摘要
The properties of three mutants of the industrial-scale L-lysine–producing strain Corynebacterium glutamicum VKPM B-11969 were studied. These mutants had one of the anaplerotic pathways for synthesizing lysine precursors, oxaloacetate, blocked due to inactivation of the ppc (encodes phosphoenolpyruvate carboxylase) or pyc (encodes pyruvate carboxylase) genes, or one of the pyruvate synthesis pathways was disrupted due to inactivation of the pyk gene (encodes pyruvate kinase). Inactivation of pyruvate carboxylase, which catalyzes the synthesis of oxaloacetate from pyruvate and CO2, did not affect L-lysine production. Inactivation of pyruvate kinase, which catalyzes the synthesis of pyruvate from phosphoenolpyruvate, resulted in a decrease in the rate of L-lysine synthesis (by 20–25%). The synthesis of L-lysine decreased to the greatest extent with the inactivation of phosphoenolpyruvate carboxylase, by 30–50% depending on the growing conditions. It was concluded that, in the B-11969 strain, under conditions of active synthesis of L‑lysine, the formation of oxaloacetate occurs predominantly with the participation of phosphoenolpyruvate carboxylase. However, the increase in the expression of the ppc gene in the producer strain led to an increase in the activity of phosphoenolpyruvate carboxylase, but not in the production of L-lysine, which allowed us to assume that in the B-11969 strain the stage of oxaloacetate synthesis is not limiting for the production of lysine.