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Expression, purification, and characterization of a novel laccase from Setosphaeria turcica in Eschericha coli

Laccases are multicopper oxidases (E.C. 1.10.3.2) that catalyze the oxidation of many phenolic compounds. In this study, a novel laccase, Stlac4, from Setosphaeria turcica was cloned and expressed in Escherichia coli by insertion into the pET‐30a expression plasmid. The recombinant laccase was purified and visualized on SDS–PAGE as a single band with an apparent molecular weight of 71.5 KDa, and confirmed by Western blot. The maximum activity of the purified laccase was 127.78 U · mg−1, the optimum temperature and pH value were 60 °C and 4.0 respectively, measured by oxidation of 2,2′‐Azinobis‐(3‐ethylbenzthiazoline‐6‐sulphonate) (ABTS). Purified laccase activity under different metal ions and an inhibitor were tested, revealing that laccase activity increased by approximately 434.8% with Fe3+, and 217.4% with Cu2+ at 10 mmol · L−1 concentrations, Mn2+ increased the laccase activity only at 5 mmol · L−1, while Na+ increased activity at 1 mmol · L−1 but inhibited activity at 5 and 10 mmol · L−1. SDS increased laccase activity at 1 mmol · L−1, and inhibited activity at 5 and 10 mmol · L−1.