Background:
Laccase has been considered important for the degradation of lignocellulose by wood rot fungi. The
properties and functions of laccase in white rot fungi have been investigated extensively, but those from brown
rot fungi remain largely unknown. In this paper, a laccase isoform Pplcc2 from the brown rot fungus
Postia placenta
MAD-698-R was expressed heterologously in Pichia pastoris GS115, purified and the properties of the
enzyme were determined.
Results:
The molecular weight of the protein was determined to be 67 kDa using SDS-PAGE. It cannot oxidize
syringaldazine (SGZ), but it can oxidize 2,2′-azino-di-(3-ethylbenzothialozin-6-Sulfonic acid) (ABTS) and
2,6-dimethoxyphenol (DMP). Specific activity for ABTS was 1960 ± 19 Unit/mg. The catalytic constant (k
cat)
was 1213 ± 18.3 s
-1 for ABTS and 293.2 ± 21.9 s
-1 for DMP. K
m was 22.08 μM for ABTS and 11.62 μM for DMP.
The optimal pH for the oxidation of ABTS and DMP was 3.5 and 5.0 respectively. The optimal temperature for
the oxidation of ABTS and DMP was 60°C.
Conclusions:
This is the first identified thermo activated and thermostable laccase in brown rot fungi. This
investigation will contribute to understanding the roles played by laccases in brown rot fungi.
