, Volume 63, Issue 5, pp 560-563
Date: 18 Sep 2003

Purification and characterization of laccase from the white-rot fungus Daedalea quercina and decolorization of synthetic dyes by the enzyme

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The white-rot fungus Daedalea quercina produced the ligninolytic enzymes laccase and Mn-dependent peroxidase. Laccase was purified using anionexchange and size-exclusion chromatographies. SDS-PAGE showed the purified laccase to be a monomeric protein of 69 kDa (71 kDa using gel filtration) with an isoelectric point near 3.0. The optimum pH for activity was bellow 2.0 for 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (K m=38 μM), 4.0 for 2,6-dimethoxyphenol (K m=48 μM), 4.5 for guaiacol (K m=93 μM) and 7.0 for syringaldazine (K m=131 μM). The temperature optimum was between 60 and 70 °C depending on the pH and buffer used. The enzyme was stable up to 45 °C, and stability was higher at alkaline pH. Enzyme activity was increased by the addition of Cu2+ and inhibited by Mn2+, sodium azide, dithiothreitol, and cysteine. Laccase from Daedalea quercina was able to decolorize the synthetic dyes Chicago sky blue, poly B-411, remazol brilliant blue R, trypan blue and reactive blue 2.