Aspartate-semialdehyde dehydrogenase Mutations for L-lysine Productivity

The patent applies parameter changes by substituting specific amino acids at positions 35, 39, and 78 in the asd gene encoding aspartate-semialdehyde dehydrogenase. These point mutations modify the enzyme's kinetic parameters and catalytic efficiency, transforming it from a suboptimal state to an enhanced state. The mutations specifically improve the enzyme's ability to catalyze the conversion of 4-aspartyl phosphate to aspartate 4-semialdehyde, directly addressing the enzyme activity optimization issue while maintaining increased L-lysine production.

The patent applies preliminary action by identifying and mutating specific amino acid positions (35, 39, and 78) in the asd gene based on prior knowledge of enzyme structure and function. Instead of conducting extensive systematic studies on all possible protein modifications, the researchers targeted specific positions that are known to be critical for enzyme activity. This approach allows them to achieve optimized enzyme activity and improved L-lysine production efficiency without requiring extensive time-consuming comprehensive studies.

The patent applies local quality by making targeted point mutations at specific amino acid positions (35, 39, and 78) in the asd gene rather than performing comprehensive genetic modifications throughout the entire gene. Each position was selected based on its specific importance to enzyme function, allowing the researchers to enhance enzyme activity locally at these critical positions while leaving the rest of the gene intact. This approach achieves the desired 3% to 40% increase in L-lysine productivity with minimal genetic modification complexity.