Synthesis of L-Tyrosine or 3, 4-Dihydroxyphenyl-L-alanine from DL-Serine and Phenol or Pyrocathechol

Abstract

Reaction conditions for the synthesis of L-tyrosine or L-dopa from DL-serine and phenol or pyrocatechol were studied with intact cells of Erwinia herbicola (ATCC 21434) containing high tyrosine phenol lyase activity. The optimum pH for this reaction was around 8.0, and the optimum temperature range was between 37_??_40°C for the synthesis of L-tyrosine and between 15_??_25°C for that of L-dopa. Sodium sulfite and EDTA were added to protect the synthesized L-dopa from decomposition. As high concentrations of phenol or pyrocatechol denatured the enzyme, each substrate was fed to maintain the optimum concentration during incubation.
The reaction mixture (100ml) containing 4.0g of DL-serine, 1.0g of phenol or 0.7g of pyrocatechol, 0.5g of ammonium acetate and the cells, was incubated. During incubation, phenol or pyrocatechol was fed at intervals to maintain the substrate at the initial concentration. 5.35g of L-tyrosine or 5.10g of L-dopa was synthesized in 100ml of the reaction mixture.