Biochemical characterization of a novel laccase from the basidiomycete fungus Cerrena sp. WR1

Abstract

This study reports a new white-rot fungus Cerrena sp. WR1, identified based on an 18S rDNA sequence, which can secrete extracellular forms of laccase with a maximal activity reaching 202 000 U l⁻¹ in a 5-l fermenter. A laccase protein, designated Lcc3, was purified and shown to be N-linked glycosylated by PNGase F and liquid chromatography tandem mass spectrometry analyses. The respective full-length cDNA gene (lcc3) of the Lcc3 protein was obtained using polymerase chain reaction-based methods. Kinetic studies showed that the K(m) and k(cat) of the native Lcc3 were 3.27 μM and 934.6 s⁻¹ for 2,2'-Azino-bis-(3-ethylbenzthiazoline-6-sulfonic acid), 849.1 μM and 147.9 s⁻¹ for guaiacol, 392.7 μM and 109.2 s⁻¹ for 2,6-dimethoxyphenol, and 881 μM and 115.5 s⁻¹ for catechol, respectively. The T(m) of Lcc3 was determined at 73.9°C and it showed a long t(½) (120 min) at 50°C. The laccase was highly ethanol resistant, with 80% of its original activity was detected when incubated in 25% ethanol for 14 days. Furthermore, crude enzyme broth or Lcc3 could degrade lignin in kraft paper (26.5%), and showed high decoloration efficiency (90%) on synthetic dye Remazol Brilliant Blue R. Together, these data demonstrate that Cerrena sp. WR1 Lcc3 possesses novel biochemical and kinetic properties that may aid its application in industry.