Effect of gluconic acid as a secondary carbon source on non-growing L-lysine producers cells of Corynebacterium glutamicum. Purification and properties of 6-phosphogluconate dehydrogenase

摘要

We studied the production of L-lysine in Corynebacterium glutamicum atcc 21543 non growing cells obtained by nutrient limitation. Statistical analysis revealed significant differences in the L-lysine titers of glucose, gluconic acid or glucose-gluconic acid cultures. Higher L-lysie titer obtained in batch cultures with mixed carbon sources or gluconic acid alone were found to be associated with a high 6-phosphogluconate dehydrogenase activity (6PGDH,E.C.1.1.1.44).This enzyme is a pivotal enzyme within the hexose monophosphate pathway, and thus of importance for L-lysine production. 6PGDH was purified ad characterized. The purified enzyme migrates as a single band on sodium dodecyl sulfate-polacrylamide gel electrophoresis with molecular mass of 52.5 kDa. The molecular mass of the native sequence shows a strong similarity (a match of 86% of the first 20 amino acid) to the 6PGDH from other microorganisms such as, E.coli and B.subtilis. The pI of the dimeric native enzyme and the optimum pH were 6.2 and 8.0, respectively. For the oxidative decarboxylation of 6-phosphogluconate, K_m of 71 #mu#M and 43 #mu#M were obtained for 6-phosphogluconate and NADP~+, respectively.