Genetically modifying aspartate aminotransferase and aspartate ammonia-lyase affects metabolite accumulation in l-lysine producing strain derived from Corynebacterium glutamicum ATCC13032

• Native AAT is necessary to cell growth and l-lysine production.
• Native AAT is sufficient to cell growth and l-lysine production.
• Expression of E. coli AAL restores the cell growth in aspB-deleted strain.
• Expression of E. coli AAL excretes more metabolites in aspB-deleted strain.
• The role of AAL on l-lysine production is worse than that of AAT.

The aspartate aminotransferase (AAT) and aspartate ammonia-lyase (AAL) catalyzes respectively the reversible reaction of oxaloacetate (OAA) and fumarate to form l-aspartate. However, the effects of AAT and AAL on metabolite variations have not been clearly elucidated as yet. Now, the effects of AAT and AAL on metabolite variations in genetically defined l-lysine producing strains were studied by genetically modifying AAT gene aspB and AAL gene aspA. AAL was not detected in Corynebacterium glutamicum Lys1 but increased in aspB-deleted strain. Inversely, AAT exhibited high activity in Lys1, but it was not detected in aspB-deleted strains. Moreover, the deletion of aspB was bad for cell growth and metabolites production. The expression of Escherichia coli aspA in aspB-deleted strain not only restored cell growth and l-lysine production, but also accumulated some metabolites. However, the over-expression of aspB or aspA in aspB-natural strain did not affect cell growth and metabolites production except l-aspartate production. Although E. coli AAL could used to restore cell growth and metabolites accumulation in aspB-deleted strain, the effect on l-lysine production was significantly worse than that of AAT. Results indicates that native AAT is both necessary and sufficient for cell growth and l-lysine production, and deepens our understanding of the role of native aspB and E. coli aspA on cell growth and metabolites productions.

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