Overproduction of L-lysine from methanol by Methylobacillus glycogenes derivatives carrying a plasmid with a mutated dapA gene

The dapA gene, encoding dihydrodipicolinate synthase (DDPS) partially desen sitized to inhibition by L-lysine, was cloned from an L-threonine- and L-ly sine-coproducing mutant of the obligate methylotroph methylobacillus glycog enes DHL122 by complementation of the nutritional requirement of an Escheri chia coli dapA mutant. Introduction of the dapA gene into DHL122 and AL119, which is the parent of DHL122 and an L-threonine producing mutant, elevate d the specific activity of DDPS 20-fold and L-lysine production 2- to 3-fol d with concomitant reduction of L-threonine in test tube cultures. AL119 co ntaining the dapA gene produced 8 g of L-lysine per liter in a 5-liter jar fermenter from methanol as a substrate. Analysis of the nucleotide sequence of the dapA gene shows that it encodes a peptide with an M-r of 30,664 and that the encoded amino acid sequence is extensively homologous to those of other organisms. In order to study the mutation that occurred in DHL122, t he dapA genes of the with type and AL119 were cloned and sequenced. Compari son of the nucleotide sequences of the dapA genes revealed that the amino a cid at residue 88 was F in DHL122 whereas it was L in the wild type and AL1 19, suggesting that this amino acid alteration that occurred in DHL122 caus ed the partial desensitization of DDPS to the inhibition by L-lysine. The s imilarity in the amino acid sequences of DDPS in nl. glycogenes and other o rganisms suggests that the mutation of the dapA gene in DHL122 is located i n the region concerned with interaction of the allosteric effector, L-lysin e .