MOLECULAR CONTROL MECHANISMS OF LYSINE AND THREONINE BIOSYNTHESIS IN AMINO ACID-PRODUCING CORYNEBACTERIA - REDIRECTING CARBON FLOW

Threonine and lysine are two of the economically most important essent ial amino acids. They are produced industrially by species of the gene ra Corynebacterium and Brevibacterium. The branched biosynthetic pathw ay of these amino acids in corynebacteria is unusual in gene organizat ion and in the control of key enzymatic steps with respect to other mi croorganisms. This article reviews the molecular control mechanisms of the biosynthetic pathways leading to threonine and lysine in coryneba cteria, and their implications in the production of these amino acids. Carbon flux can be redirected at branch points by gene disruption of the competing pathways for lysine or threonine. Removal of bottlenecks has been achieved by amplification of genes which encode feedback res istant aspartokinase and homoserine dehydrogenase (obtained by in vitr o directed mutagenesis).