Formation of biodegradative threonine deaminase in Escherichia coli.

Studies were carried out on the formation of biodegradative L-threonine deaminase (EC 4.2.1.16) in resting cells of Escherichia coli. The results obtained are as follows: (1) The enzyme level was increased by adding L-threonine together with yeast extract to the cell suspension. (2) In the course of the enzyme formation, the addition of chloramphenicol or glucose to the medium resulted in instantaneous cessation of the enzyme synthesis. (3) Yeast extract could be partially replaced by casamino acids. A mixture of amino acids whose composition is similar to that of milk casein was also effective. (4) Omission of L-serine from the mix ture caused an almost complete loss of the activity, indicating that L serine as well as L-threonine was essentially required for the enzyme formation. (5) Other amino acids were also needed for the enzyme synthesis, although individual omission of them had a slight influence compared with that of L-serine.