Abstract
Typical laccases have four copper atoms, which form three different copper centers, of which the T1 copper is responsible for the blue color of the enzyme and gives it a characteristic absorbance around 610 nm. Several laccases have unusual spectral properties and are referred to as yellow or white laccases. Only two yellow laccases from the Ascomycota phylum have been described previously, and only one amino acid sequence of those enzymes is available. A yellow laccase Bcl1 from Botrytis cinerea strain 241 has been identified, purified and characterized in this work. The enzyme appears to be a dimer with a molecular mass of 186 kDa. The gene encoding the Bcl1 protein has been cloned, and the sequence analysis shows that the yellow laccase Bcl1 is phylogenetically distinct from other known yellow laccases. In addition, a comparison of amino acid sequences, and 3D modeling shows that the Bcl1 laccase lacks a conservative tyrosine, which is responsible for absorption quenching at 610 nm in another yellow asco-laccase from Sclerotinia sclerotiorum. High thermostability, high salt tolerance, broad substrate specificity, and the ability to decolorize dyes without the mediators suggest that the Bcl1 laccase is a potential enzyme for various industrial applications.
Highlights
IntroductionLaccases (benzenediol: oxygen oxidoreductase; E.C. 1.10.3.2) oxidize a great variety of aromatic compounds [1,2]
Laccases oxidize a great variety of aromatic compounds [1,2]
Methyl syringate purchased from Lancaster Synthesis, Ward Hill, MA, USA, was recrystallized from ethanol. 2,6-dimethoxyphenol was obtained from Alfa Aesar, Kandel, Germany
Summary
Laccases (benzenediol: oxygen oxidoreductase; E.C. 1.10.3.2) oxidize a great variety of aromatic compounds [1,2]. Mot and co-authors identified the binding site—the compound covalently binds to the tyrosine residue site at the T1 center and turns laccase from blue to yellow [18,29]. Each Botrytis spp. strain can produce several laccase isoenzymes of rather different physico-chemical features [32,33,34,35,36,37,38]. Such abundance of laccases produced by these fungi is not surprising, as 15 genes encoding laccases have been identified in the genome of B. cinerea [39,40]. We presented data on biochemical and catalytic properties of the Bcl enzyme including the de-colorization of some synthetic dyes
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