The ilvEDA operon of Escherichia coli K12 encodes only one valine-alpha-ketoglutarate transaminase activity.

Transaminase B of $\text{E. coli}$ K12 was purified to apparent homogeneity as measured by SDS acrylamide gel electrophoresis, immunoelectrophoresis, and amino terminal sequence analysis. The valine- and isoleucine-α-ketoglutarate dependent transaminase activities of pure enzyme as well as crude extracts were characterized by immunologic and kinetic methods. The data disprove the existence of a separate valine-α-ketoglutarate transaminase within the $\text{ilvEDA}$ operon.