Purification and properties of Neurospora crassa laccase

Extracellular Neurospora laccase (p-diphenol:oxygen oxidoreductase; EC 1.10.3.2) has been purified to apparent homogeneity by classical purification techniques. The enzyme, which consists of mainly one form, has a molecular weight of 64,800 and contains 11% carbohydrate. The ultraviolet, visible, and electron paramagnetic resonance spectra indicate that both type I and type II copper are present, as described for the Polyporus versicolor enzyme. With the exception of phloroglucinol, only para- and ortho-diphenols serve as effective substrates for the enzyme. Like the extracellular form, intracellular laccase is a glycoprotein as shown by its ability to bind to Concanavalin A Sepharose. Other studies, including gel filtration and ion-exchange chromatography, revealed no differences between the intracellular and extracellular enzymes, suggesting that intracellular laccase is destined for excretion by the cell.