Characterization of a recombinant tannase from Pseudoduganella albidiflava with high substance affinity for propyl gallate

Tannase have broad practical applications in the food, feed, agriculture and leather industries. In this study, a putative tannase (Pa-Tan) from P. albidiflava was identified and characterized. The enzyme was expressed in Escherichia coli and purified using metal-affinity chromatography. Purified recombinant tannase had the highest activity at pH 6.0 and 30°C. The Pa-Tan maintained >70% residual activity at pH 6.0-8.0 and approximately 90% of its maximum activity was retained after incubating at 30°C for 1 h. The addition of low concentrations of Ba2+, Li+, and DMSO could slightly stimulate the enzymatic activity of Pa-Tan, whereas Cu2+, Fe3+, Hg2+, SDS, DTT, and β-mercaptoethanol heavily inhibited the enzymatic activity of Pa-Tan. Meanwhile, the kinetic parameters of Pa-Tan were determined for methyl gallate, propyl gallate, and tannic acid as substrates. The estimated Km, kcat, and kcat/Km values were 0.27 mM, 5.48 s−1, 20.37 s−1 mM−1 for methyl gallate, 0.09 mM, 4.97 s−1, 53.50 s−1 mM−1 for propyl gallate, and 0.48 mM, 71.58 s−1, 149.62 s−1 mM−1 for tannic acid, respectively. Pa-Tan has a high affinity for substrates, particularly propyl gallate, which gives it a high potentiality for industrial applications.