____________________ *Corresponding author: e-mail: adikunamneni@rediffmail.com, Phone: +34 915855479 Fungal laccase – a versatile enzyme for biotechnological applications Adinarayana Kunamneni*, Antonio Ballesteros, Francisco J. Plou and Miguel Alcalde Departamento de Biocatálisis, Instituto de Catálisis y Petroleoquímica, CSIC, 28049—Madrid, Spain. Laccase belongs to the small group of enzymes called the blue multi copper oxidases. Laccase is widely distributed in higher plants and fungi. In fungi, laccase is present in Ascomycetes, Deuteromycetes, Basidiomycetes and is particularly abundant in many white-rot fungi that degrade lignin. Laccases have been subject of intensive research in the last decades due to their broad substrate specificity. In the recent years, their uses span from the textile to the pulp and paper industries, and food applications to bioremediation processes. Laccases also have uses in organic synthesis, where typical substrates are phenols and amines, and the reaction products are dimers and oligomers derived from the coupling of reactive radical intermediates. More recently, they have found applications in other field such as in the design of biosensors and biofuel cells. In this review, the occurrence, mode of action, general properties, production and immobilization of laccases will be discussed. Here, we will also provide discussion of potential applications of these blue enzymes. Keywords Laccase, White rot fungi, Production, Properties, Potential applications, Pulp and paper industry, Textile industry, Food industry, Bioremediation, Organic syntheses, Biosensors, Biofuel cells 1. Introduction Laccase (benzenediol:oxygen oxidoreductase, EC 1.10.3.2) belongs to the small group of enzymes called the blue copper proteins or the blue copper oxidases along with the plant ascorbate oxidase and the mammalian plasma protein ceruloplasmin [1,2] among others. These proteins are characterized by containing 4 catalytic copper atoms. One copper is placed at the T1 site, where reducing substrate binds, and it is responsible in the characteristic blue-greenish colour in the oxidizing resting state Cu 2+ [1,3]. The other three coppers are clustered in the called T2/T3 site in which molecular oxygen binds. Laccase is widely distributed in higher plants and fungi [4] and has been found also in insects and bacteria. Recently a novel polyphenol oxidase with laccase like activity was mined from a metagenome expression library from bovine rumen microflora [5]. Yoshida first described laccase in 1883 when he extracted it from the exudates of the Japanese lacquer tree, Rhus vernicifera [1,6]. In 1896 laccase was demonstrated to be present in fungi for the first time by both Bertrand and Laborde [1,6]. Since then, laccases have been found in Ascomycetes, Deuteromycetes and Basidiomycetes; being particularly abundant in many white-rot fungi that are involved in lignin metabolism [7,8]. Fungal laccases have higher redox potential than bacterial or plant laccases (up to +800 mV), and their action seems to be relevant in nature finding also important applications in biotechonology. Thus, fungal laccases are involved in the degradation of lignin or in the removal of potentially toxic phenols arising during lignin degradation [1]. In addition, fungal laccases are hypothesized to take part in the synthesis of dihydroxynaphthalene melanins, darkly pigmented polymers that organisms produce against environmental stress [9] or in fungal morphogenesis by catalysing the formation of extracellular pigments [10]. Concerning their use in the biotechnology area, fungal laccases have widespread applications, ranging from effluent decolouration and detoxification to pulp bleaching, removal of phenolics from wines, organic synthesis, biosensors, synthesis of complex medical compounds and dye transfer blocking functions in detergents and washing powders, many of which have been patented [11]. The biotechnological use of laccase has been expanded by the introduction of laccase-mediator systems, Communicating Current Research and Educational Topics and Trends in Applied Microbiology A. Méndez-Vilas (Ed.) 233 ©FORMATEX 2007 _____________________________________________________________________