Detoxification of azo dyes by a novel pH-versatile, salt-resistant laccase from Streptomyces ipomoea Molina-Guijarro, José M. Pérez Torres, Juana Muñoz Dorado, José Guillén Carretero, Francisco Moya Lobo, Raquel Hernández Cutuli, Manuel Arias Fernández, María Enriqueta Streptomyces ipomoea Laccases Azo-dye detoxification A newly identified extracellular laccase produced by Streptomyces ipomoea CECT 3341 (SilA) was cloned and overexpressed, and its physicochemical characteristics assessed together with its capability to decolorize and detoxify an azotype dye. Molecular analysis of the deduced sequence revealed that SilA contains a TAT-type signal peptide at the N-terminus and only two cupredoxine domains; this is consistent with reports describing two other Streptomyces laccases but contrasts with most laccases, which contain three cupredoxine domains. The heterologous expression and purification of SilA revealed that the homodimer is the only active form of the enzyme. Its stability at high pH and temperature, together with its resistance to high concentrations of NaCl and to typical laccase inhibitors such as sodium azide confirmed the unique properties of this novel laccase. The range of substrates that SilA is able to oxidize was found to be pH-dependent; at alkaline pH, SilA oxidized a wide range of phenolic compounds, including the syringyl and guayacil moieties derived from lignin. The oxidative potential of this enzyme to use phenolic compounds as natural redox mediators was shown through the coordinated action of SilA and acetosyringone (as mediator), which resulted in the complete detoxification of the azo-type dye Orange II. 2014-09-19T08:59:04Z 2014-09-19T08:59:04Z 2009 journal article Molina-Guijarro, J.M.; et al. Detoxification of azo dyes by a novel pH-versatile, salt-resistant laccase from Streptomyces ipomoea. International Microbiology, 12: 13-21 (2009). [http://hdl.handle.net/10481/33093] 1139-6709 http://hdl.handle.net/10481/33093 10.2436/20.1501.01.77 eng http://creativecommons.org/licenses/by-nc-nd/3.0/ open access Creative Commons Attribution-NonCommercial-NoDerivs 3.0 License Sociedad Española de Microbiología