Metabolic Engineering of Escherichia coli for L-Tyrosine Production by Expression of Genes Coding for the Chorismate Mutase Domain of the Native Chorismate Mutase-Prephenate Dehydratase and a Cyclohexadienyl Dehydrogenase from Zymomonas mobilis

The expression of the feedback inhibition-insensitive enzyme cyclohexadienyl dehydrogenase (TyrC) from Zymomonas mobilis and the chorismate mutase domain from native chorismate mutase-prephenate dehydratase (PheACM) from Escherichia coli was compared to the expression of native feedback inhibition-sensitive chorismate mutase-prephenate dehydrogenase (CM-TyrAp) with regard to the capacity to produce L-tyrosine in E. coli strains modified to increase the carbon flow to chorismate. Shake flask experiments showed that TyrC increased the yield of L-tyrosine from glucose (YL₋Tyr/Glc) by 6.8-fold compared to the yield obtained with CM-TyrAp. In bioreactor experiments, a strain expressing both TyrC and PheACM produced 3 g/liter of L-tyrosine with a YL₋Tyr/Glc of 66 mg/g. These values are 46 and 48% higher than the values for a strain expressing only TyrC. The results show that the feedback inhibition-insensitive enzymes can be employed for strain development as part of a metabolic engineering strategy for L-tyrosine production.