Characterization of a laccase in the conidial mucilage of Colletotrichum graminicola

A polyphenol oxidase was demonstrated to be a component of the extracellular conidial mucilage of Colletotrichum graminicola. The enzyme was identified as a laccase based on its oxidation of syringaldazine in the absence of hydrogen peroxide and its absorption maximum at 593 nm, that is characteristic of blue, type II copper-containing laceases. The enzyme, purified by DEAE cellulose, Superose and MONO Q Fast Protein Liquid chromatographic procedures, had a molecular weight of 85 kD, a pH optimum of 6.0, and exhibited Km and Vmax values of 0.214 mmoles and 1.014 mmoles L-1 min-1, respectively, with syringaldazine as the substrate. The function of the enzyme is discussed relative to its potential role in fungal survival and detoxification of plant phenols.