Effective production of 3,4-dihydroxyphenyl- l-alanine ( l-DOPA) with Erwinia herbicola cells carrying a mutant transcriptional regulator TyrR

The enzymatic production of 3,4-dihydroxyphenyl- l-alanine ( l-DOPA) using Erwinia herbicola cells involves the action of tyrosine phenol-lyase (Tpl, EC 4.1.99.2). Since Tpl is only synthesized under l-tyrosine-induced conditions, the addition of l-tyrosine to the medium is unavoidable when preparing cells (the enzyme source), but severely impedes the pure preparation of the final product l-DOPA. We circumvented this problem by using recombinant E. herbicola cells carrying a mutant transcriptional regulator TyrR, which is capable of activating the tpl promoter in the absence of l-tyrosine.