Purification and Characterization of a Novel Laccase from the Edible Mushroom Hericium coralloides

A novel laccase from the edible mushroom Hericium coralloides was purified by ion exchange chromatography on diethylaminoethyl (DEAE) cellulose, carboxymethyl (CM) cellulose, and Q-Sepharose columns followed by fast protein liquid chromatography gel filtration on a Superdex 75 column. Analysis by gel filtration and SDS-PAGE indicated that the protein is a monomer in solution with a molecular mass of 65 kDa. Its N-terminal amino acid sequence was AVGDDTPQLY, which exhibits partial sequence homology to previously isolated laccases. Optimum activity was observed at pH 2.2 and at 40 degrees C. The enzyme showed activity toward a variety of substrates, the most sensitive of which was 2,2'-azinobis [3-ethylbenzothiazolone-6-sulfonic acid] diammonium salt (ABTS). The degradation activity toward substrates was ABTS > N,N-dimethyl-1,4-phenylenediamine > catechol > 2-methylcatechol > pyrogallol. The laccase did not exert any antiproliferative activity against Hep G2 or MCF 7 tumor cell lines at a concentration of 60 mu M, unlike some previously reported mushroom proteins, but showed significant activity toward human immunodeficiency virus-1 (HIV-1) reverse transcriptase with an IC50 of 0.06 mu M.