The 279th residue of aspartate kinase in Corynebacterium glutamicum is important for relieving the feedback inhibition by L-lysine and L-threonine.

• The 279th residue of CgAK is important for relieving inhibition by L-lysine. • CgAKA279D shows the high degree of desensitization for L-lysine. • CgAKA279D benefits to increase the efficiency of L-lysine production. Aspartate kinase (AK) is the key rate-limiting enzyme for producing aspartate-family amino acids, but it is inhibited by products. In this study, a desensitizing CgAK variant was created and was used to increase L-lysine production in Corynebacterium glutamicum. To do this, different CgAK variants from different L-lysine producing strains were investigated through sequence alignment and functional analysis indicating that the 279th residue in CgAK plays important roles in relieving the inhibition by L-threonine and L-lysine, thus affecting the biosynthesis of L-lysine. Subsequently, the amino acid residue at 279th site was mutated by site-saturation mutagenesis and indicated that CgAKA279D showed the higher degree of desensitization of inhibition by L-lysine and L-lysine plus L-threonine than that of the other CgAK variants because replacement of the Ala at 279th site by Asp in CgAK reduces the interactions between inhibitors and CgAK. The results of L-lysine fermentation in fed-batch fermentation showed that the resultant strain LYS-279D with overexpression of CgAKA279D produced 172.3 g/L of L-lysine with a productivity of 2.39 g/(L·h) and the glucose conversion efficiency (α) of 47.74 %, which were higher than that of strain LYS-279T (i.e., 153.4 g/L, 2.13 g/(L·h) and 41.44 %, respectivley). These findings provide a reference for constructing a desensitizing CgAK variant with high enzyme activity and reconfirm that CgAK is key enzyme for L-lysine production. [Display omitted] [ABSTRACT FROM AUTHOR]