In wild-type C. glutamicum, aspartokinase is subject to concerted feedback inhibition by both lysine AND threonine simultaneously. Mutations creating a feedback-insensitive aspartokinase allow carbon flux to continue through the aspartate pathway even when lysine accumulates. Additional engineering includes deletion of competing branches (homoserine dehydrogenase to block threonine synthesis), amplifying lysine-specific enzymes. This rational metabolic engineering produces >100 g/L lysine.