The threonine-sensitive homoserine dehydrogenase and aspartokinase activities of Escherichia coli

Abstract

• 1.

  1. Homoserine dehydrogenase I (l-homoserine:NADP⁺ oxidoreductase, EC 1.1.1.3) of Escherichia coli is inactivated with apparent first-order kinetics by exposure at pH 9 in Tris buffer. This inactivation is accompanied by desensitization of the enzyme towards threonine.

• 2.

  2. L-Aspartate and ATP, the substrates of the associated activity, β-aspartokinase I (ATP:L-aspartate 4-phosphotransferase, EC 2.7.2.4) protect against the desensitization of homoserine dehydrogenase.