Cell suspension cultures of Portulaca grandiflora as potent catalysts for biotransformation of L-tyrosine into L-DOPA, an anti-Parkinson's drug

Abstract

3,4-Dihydroxy L-phenylalanine (L-DOPA) is considered a potent drug for the treatment of Parkinson disease, a neurologic disorder. Enantiomerically pure L-DOPA is produced from L-tyrosine in a single-step biotransformation process using callus cultures of the plant Portulaca grandiflora Hook (Portulacaceae). Callus cultures were induced in MS medium provided with growth regulators such as benzylaminopurine (BA; 1.5 mg L-1) and 2,4-dichlorophenoxyacetic acid (2,4-D; 0.1 mg L-1) and were found to be an excellent source of tyrosinase, which in turn was used for the biotransformation of L-tyrosine into L-DOPA. A culture time of 20-25 days was found to be optimum for biomass production, and the tyrosinase activity in the medium was found to be 2.19 U/mL. Optimization of L-DOPA production was carried out by varying the concentration of BA and 2,4-D. In view of the fact that the enzyme tyrosinase has a dicopper catalytic site, the concentration of Cu2+ was manipulated in the media to study its impact on biotransformation rate. The L-DOPA was purified by column chromatography and the analysis was done by TLC, HPLC, FT IR, and MS. The optimized production of L-DOPA, 48.8 mg L-1 h-1, is one of the highest values recorded in the literature. © 2007 Informa Healthcare.