Tyrosine decarboxylase from Lactobacillus brevis: Soluble expression and characterization

Tyrosine decarboxylase (TDC, EC 4.1.1.25) is an enzyme that catalyzes the decarboxylation of L-tyrosine to produce tyramine and CO2. In this study, a 1881-bp tdc gene from Lactobacillus brevis was cloned and heterologously expressed in Escherichia coli BL21 (DE3). Glucose was discovered to play an important role in the soluble expression of rLbTDC. After optimization, recombinant TDC (rLbTDC) was achieved in excellent solubility and a yield of 224 mg rLbTDC/L broth. The C-terminal His-Tagged rLbTDC was onestep purified with 90% recovery. Based on SDS-PAGE and gel filtration analysis, rLbTDC is a dimer composed of two identical subunits of approximately 70 kDa. Using L-tyrosine as substrate, the specific activity of rLbTDC was determined to be 133.5 U/mg in the presence of 0.2 mM pyridoxa1-5'-phosphate at 40 C and pH 5.0. The K-m and V-max values of rLbTDC were 0.59 mM and 147.1 mu mol min(-1) mg(-1), respectively. In addition to L-tyrosine, rLbTDC also exhibited decarboxylase activity towards L-DOPA. This study has demonstrated, for the first time, the soluble expression of tdc gene from L brevis in heterologous host. (C) 2013 Elsevier Inc. All rights reserved.