Production of chorismate mutase-prephenate dehydrogenase by a strain of Escherichia coli carrying a multicopy, tyrA plasmid. Isolation and properties of the enzyme

A multicopy plasmid that contains the tyrosine operon has been used to transform strains of Escherichia coli K-12. The resultant strains yielded levels of chorismate mutase-prephenate dehydrogenase that were up to 5000-fold higher than that given by the parent strain and about 6-fold higher than that given by a tyrR strain. The production of enzyme fell when tetracycline was omitted from the growth medium because of the loss of the plasmid. The bifunctional enzyme was isolated in good yield by a simple purification procedure and shown to possess properties identical to those exhibited by the enzyme from a tyrR strain.