Tyrosine decarboxylase from Lactobacillus brevis: Soluble expression and characterization

• First report on soluble expression of tdc (encoding tyrosine decarboxylase) from Lactobacillus brevis.
• Glucose plays an important role in the soluble expression of rLbTDC.
• rLbTDC exhibits decarboxylase activity towards l-DOPA besides l-tyrosine.

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 one-step 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 pyridoxal-5′-phosphate at 40 °C and pH 5.0. The Km and Vmax values of rLbTDC were 0.59 mM and 147.1 μmol 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.