Feed-back Inhibition and Repression of Aspartokinase Activity in Escherichia coli and Saccharomyces cerevisiae

Regulation of diverse biosynthetic pathways by changes in concentrations of the ultimate end products is achieved by two distinct mechanisms: (a) a repression of the synthesis of enzymes involved in the metabolic pathway (1, 2) and (b) specific inhibition of the enzymatic activity which controls usually the first step, in the metabolic sequence (3). The first mechanism has been referred to as “repression” and the second is known as “feed-back control.” As is indicated in Scheme 1, in Escherichiu coli aspartokinase catalyzes the first step in a metabolic sequence which leads