The Threonine-Sensitive Homoserine Dehydrogenase and Aspartokinase Activities of <em>Escherichia coli</em> K12.

2-Amino-4-oxo-5-chloropentanoic acid inactivates specifically the homoserine dehydrogenase activity of the bifunctional enzyme, aspartokinase I - homoserine dehydrogenase I. The asparto-kinase activity remains essentially untouched and retains its threonine sensitivity. The inactivation of the dehydrogenase requires the covalent binding of one equivalent of the analogue per subunit. Alkylation does not affect the tetrameric state of the protein. The alkylating agent, a substrate analogue, meets the qualitative and quantitative requirements of an affinity label. [ABSTRACT FROM AUTHOR]