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This article in JEQ

  1. Vol. 28 No. 6, p. 1929-1938
     
    Received: July 31, 1998
    Published: Nov, 1999


    * Corresponding author(s): gianfred@unina.it
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doi:10.2134/jeq1999.00472425002800060032x

Effect of Various Pollutants and Soil-Like Constituents on Laccase from Cerrena unicolor

  1. M.T. Filazzola,
  2. F. Sannino,
  3. M. A. Rao and
  4. L. Gianfreda *
  1. Dipartimento di Scienze Chimico-Agrarie, Università di Napoli “Federico II,” Via Università 100, 80055 Portici (Napoli), Italy.

Abstract

Abstract

Laccase from Cerrena unicolor catalyses the oxidation of a wide range of aromatic compounds, either xenobiotic or naturally occurring phenols, leading to the formation of polymeric products. These are characterized by their low solubility and often may form precipitates or aggregates. The oxidizing efficiency of the enzyme is strictly dependent on the number of hydroxyl groups and the position of substituents on the phenolic molecules. During the reaction with some substrates, the enzyme is inactivated, because of possible adsorption of laccase molecules on newly formed polyphenols. By contrast, the oxidation of humic precursors (i.e., resorcinol, gallic acid, and pyrogallol) does not influence greatly the residual laccase activity. The triazinic herbicides, triazine and prometryn (2,4-bis(isopropylamino)-6-methylthio-s-triazine), are not substrates of laccase. They, however, inhibit laccase activity assayed with 2,4-dichlorophenol (2,4-DCP) or catechol as substrates. The reduction of substrate oxidation rates is usually accompanied by the retention of higher levels of residual enzymatic activity. These results, together with the slight recovery in laccase activity following dialysis of the assay mixture, provide further evidence that the enzyme may be incorporated into or adsorbed onto polyphenolic products, with a consequent reduction in the concentration of active forms of laccase.

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