Biomimetic synthesis of L-DOPA inspired by tyrosine hydroxylase

Abstract

L-3,4-dihydroxyphenylalanine (L-DOPA) is in high demand as the cornerstone for treatment of Parkinson's disease. The current production of L-DOPA is associated with poor productivity and long production period. Biomimetic system inspired from tyrosine hydroxylase was developed to achieve the production of L-DOPA from tyrosine with high reactivity, efficiency, and specificity. The biomimetic system owned close resemblance of component and structure in comparison with tyrosine hydroxylase, consisting of tyrosine as substrate, a redox complex of Fe²⁺ and EDTA as the catalyst to simulate the active center of the natural tyrosine hydroxylase, hydrogen peroxide as the oxidant, and ascorbic acid as the reductant. HPLC, HPLC-MS/MS, ¹H NMR, and specific rotation identified L-DOPA was generated. The system showed high catalytic activity and regioselectivity for hydroxylation of tyrosine as equal to tyrosine hydroxylase. Fe^IVO²⁺ was formed as the major active species, and NIH shift was observed. EDTA accelerated the reaction by reducing the redox potential of Fe³⁺/Fe²⁺ couple. Density functional theory calculation suggested formation of Fe^IVO²⁺ was more thermodynamically favorable. The biomimetic system shared analogous catalytic mechanism with TyrH. Process parameters was optimized for maximum production of L-DOPA, namely 6.4 mM tyrosine, 1.6 mM Fe²⁺, 1.92 mM EDTA, 150 mM H₂O₂, and 35 mM ascorbic acid in 0.2 M glycine-HCl buffer at pH 4.5 and 60 °C. The yield, titer, and productivity were obtained as 52.01%, 3.22 mM, and 48,210.68 mg L^-1 h^-1, respectively. The proposed method exhibited an amazing productivity, might provide a promising strategy to industrialize L-DOPA production.

Keywords: Biomimetic synthesis; EDTA; Fe(2+); Hydroxylase; L-DOPA; Tyrosine.