RESUMEN

Laccases are oxidizing enzymes of interest because of their potential environmental and industrial applications. We performed site-directed mutagenesis of a laccase produced by Trametes versicolor in order to improve its catalytic properties. Considering a strong interaction of the Asp residue in position 206 with the substrate xylidine, we replaced it with Glu, Ala or Asn, expressed the mutant enzymes in the yeast Yarrowia lipolytica and assayed the transformation of phenolic and non-phenolic substrates. The transformation rates remain within the same range whatever the mutation of the laccase and the type of substrate: at most a 3-fold factor increase was obtained for k(cat) between the wild-type and the most efficient mutant Asp206Ala with 2,2'-azinobis(3-ethylbenzthiazoline-6-sulfonic) acid as a substrate. Nevertheless, the Asn mutation led to a significant shift of the pH (DeltapH = 1.4) for optimal activity against 2,6-dimethoxyphenol. This study also provides a new insight into the binding of the reducing substrate into the active T1 site and induced modifications in catalytic properties of the enzyme.

Asunto(s)

Lacasa/genética , Lacasa/metabolismo , Polyporales/enzimología , Polyporales/genética , Secuencia de Aminoácidos , Compuestos de Anilina/metabolismo , Secuencia de Bases , Dominio Catalítico , ADN de Hongos/genética , Concentración de Iones de Hidrógeno , Cinética , Lacasa/química , Modelos Moleculares , Datos de Secuencia Molecular , Mutagénesis Sitio-Dirigida , Ingeniería de Proteínas , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Homología de Secuencia de Aminoácido , Especificidad por Sustrato , Yarrowia/enzimología , Yarrowia/genética