Molecular properties of extracellular Botrytis cinerea laccase

Two molecular forms of extracellular laccase induced by different phenolics were studied in Botrytis cinerea. The enzyme induced by grapejuice had a MW of 38 000 and contained 80 % sugar while that induced by gallic acid had a MW of 36 000 and contained 70 % sugar. Both forms contained arabinose, xylose, mannose, galactose and glucose but differed markedly in the relative content of these sugars. Tunicamycin, which inhibits glycosylation of peptide chains, considerably reduced the level of laccase in both hyphae and medium. The two enzyme forms differed also in their isoelectric focusing pattern and amino acid composition, the grape juice enzyme being richer in basic amino acids and poorer in acidic ones. A third form, induced by p-coumaric acid, resembled the laccase induced by gallic acid in many of its properties but was apparently not identical to it. The possible significance of the various forms in relation to the infection process by the fungus is discussed.