Purification, Biochemical Characterization and Applications of Pleurotus ostreatus ARC280 Laccase

Aims: To purify, characterize, and apply the laccase produced by submerged fermentation using an edible mushroom Pleurotus ostreatus ARC280.

Study Design: Laccase purification and characterization were designed using the most recent approaches and statistical studies of triplicate results values.

Place and Duration of Study: Department of Microbial Chemistry, Genetic Engineering and Biotechnology Division, National Research Centre, Dokki, Cairo, Egypt, between May 2011 and January 2013.

Methodology: P. ostreatus ARC280 laccase was purified using ammonium sulfate precipitation (40-80%), followed by gel filtration using Sephadex G100 column chromatography. The resulted pure laccase was analyzed on SDS-PAGE (12%). Laccase activity parameters such as temperature, pH, stability, metal ions and kinetic constants were studied. Laccase was applied to reduce four tumor cell lines growth and as antibacterial and antifungal agent.

Results: P. ostreatus ARC280 laccase was purified using ammonium sulphate followed by Sephadex G-100 chromatographic column by about 148 purification fold with Mr of 85kDa. Optimum P. ostreatus ARC280 purified laccase activity was recorded at 50ºC and at pH 6.0, 3.0, 4.5 for Syringaldazine (SGZ), 2,2'-azinobis-(3-ethylbenzthiazoline-6-sulfonic) acid (ABTS) and 2, 6-dimethoxyphenol (DMP) as substrates, respectively. The purified enzyme was more stable in alkaline pH range and retained about 37.42, 73.51, 85.65, 87.7, 88.49, 93.65, 92.86 and 100.0 % of the initial activity after 5hrs of incubation at pH 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0 and 10.0, respectively. Hg2+ caused complete inhibition at all tested concentrations; however Mn2+ (2.5x10-3M) caused laccase activation by about 190 and 330% after 1 and 24 hrs, respectively. Km and Vmax were calculated and found to be 0.074, 2.857 and 0.476 µM and 1.563, 2.500 and 2.632 µmol min-1 for SGZ, DMP and ABTS, respectively. The purified enzyme has the ability to reduce four tested cell lines growth in vitro with percentage reduction of 16.8, 23.4, 15.2 and 23.4% for HePG2, HCT116, A549 and MCF7, respectively. On the other hand, the enzyme was found to have antibacterial and antifungal activities against Escherichia coli and Candida albicans respectively.

Conclusion: This enzyme seems to be a prospective enzyme for further biotechnological exploitation such as anticancer and antimicrobial activity applications.