Enzymatic catalysis of 2,6-dimethoxyphenol by laccases and products characterization in organic solutions

2,6-Dimethoxyphenol (DMP) as a substrate was widely used in determination of laccase activity. It is surprising, however, that its catalyzed oxidation products have not been completely determined until now. Studies were thus conducted on Rhus laccase (RL) and immobilized Rhus laccase (IRL)-catalyzed oxidation reactions of 2,6-dimethoxyphenol in water-organic solvent systems. These reactions proceeded well in water-(im)miscible organic solvent systems pre-saturated with water. Only one product, 3,3',5,5'-tetramethoxy-1,1'biphenyl-4,4'-diol (TMBP), was produced by RL catalysis, and it was thoroughly characterized by FT-IR, NMR, GC-MS, etc. A simple enzymatic mechanism of this reaction is proposed.