Regulation of Aspartokinase in Azotobacter Species

Aspartokinase activity was regulated by feedback inhibition in members of the genus Azotobacter. In five species the enzyme was inhibited by l-threonine and by l-lysine. The sensitivity of the enzyme to l-threonine was much higher than its sensitivity to l-lysine. Aspartokinase was also subject to concerted feedback inhibition by low concentrations of both of these amino acids. Six strains of Azotobacter chroococcum, A. vinelandii and A. beijerinckii possessed a similar regulation pattern, which differed from that found in A. macrocytogenes and A. insignis. The taxonomic value of the pattern of inhibition of aspartokinase in the genus Azotobacter and its relation to other genera is discussed.