A study on the electrochemical synthesis of L-DOPA using oxidoreductase enzymes: Optimization of an electrochemical process

Levodopa or L-3,4-dihydroxyphenylalanine (L-DOPA) is the precursor of the neurotransmitter dopamine. L-DOPA is a famous treatment for Parkinson's disease symptoms. In this study, electroenzymatic synthesis of L-DOPA was performed in a three-electrode cell, comprising a Ag/AgCl reference electrode, a platinum wire auxiliary electrode, and a glassy carbon working electrode. L-DOPA had an oxidation peak at 376 mV and a reduction peak at-550 mV. The optimum conditions of pH, temperature, and amount of free tyrosinase enzyme were pH 7, 30°C, and 250 IU, respectively. The kinetic constant of the free tyrosinase enzyme was found for both cresolase and catacholase activity to be 0.25 and 0.4 mM, respectively. A cyclic voltammogram was used to investigate the electron transfer rate constant. The mean heterogeneous electron transfer rate (ke) was 5.8 × 10^-4cm/s. The results suggest that the electroenzymatic method could be an alternative way to produce L-DOPA without the use of a reducing agent such as ascorbic acid.