Multivalent regulation of isoleucine-valine transaminase in an Escherichia coli K-12 ilvA deletion strain.

In a strain of Escherichia coli K-12 lacking threonine deaminase, the enzyme converting alpha-ketoisovalerate and alpha-keto-beta-methylvalerate to valine and isoleucine, respectively, was multivalently repressed by valine, isoleucine, and leucine. This activity was due to transaminase B, specified by the ilvE structural gene.