Purification, characterization, and gene cloning of two laccase isoenzymes (Lac1 and Lac2) from Trametes hirsuta MX2 and their potential in dye decolorization.

ABSTRACT

In this study, two laccase isoenzymes (Lac1 and Lac2) from the culture supernatant of Trametes hirsuta MX2 were purified, and the genes (Lac1 and Lac2) coding the isoenzymes were cloned. Both Lac1 and Lac2 contained an open reading frame of 1563 bp with an identity of 79%. The two isoenzymes showed significant biochemical differences. The maximal activities of Lac1 and Lac2 were at pH 2.5 with 2-2'-azino-di-(3-ethylbenzthiazoline sulfonic acid) (ABTS), and the optimal temperatures for the activities of Lac1 and Lac2 were 60 and 50 °C, respectively. Lac1 exhibited excellent resistance to acidic conditions and retained 62.17% of its initial activity at pH 2.5 after a 72-h incubation. Lac2 was more thermostable than Lac1 with half-lives (t1/2) of 9.58 and 3.12 h at 50 and 60 °C, respectively; the t1/2 of Lac1 were only 4.19 and 0.88 h, respectively. Both Lac1 and Lac2 isoenzymes have a strong tolerance to Mg2+, Mn2+, Cu2+, and EDTA (50 mM). At a low concentration of 0.05 U mL-1, the enzymes could decolorize towards Remazol Brilliant Blue R, Acid Red 1, Crystal Violet, and Neutral Red in the presence of ABTS. These unusual properties demonstrated that the two laccases have strong potential for specific industrial applications.