Laccase activity accumulated during rhizomorph development in malt extract cultures of Armillaria meffeu. The activity was readily separated into two bands by PAGE under non-denaturing conditions. The less rapidly migrating activity (on PAGE) was purified by ammonium sulphate precipitation, anion-exchange chromatography and gel filtration. The purified enzyme (laccase I) showed a main polypeptide of M,. 59000. Activity of the purified enzyme was greatest with 2,6-dimethoxyphenol (DMOP) as substrate. Syringaldazine, p-phenylenediamine and other typical laccase substrates were readily oxidized. No oxidation of tyrosine was detected. The K, for DMOP was 0.178 mM and for p-phenylenediamine was 1.69 mM. The pH optimum for pphenylenediamine oxidation was 3.5. Electrophoretically purified main polypeptide of laccase I was used to raise a specific antibody. Immunoblot analysis showed that whilst the antibody bound strongly to laccase I, no binding to laccase I1 was detectable. Antibody raised against pure laccase from Agaricus bisporus reacted with laccase I from Armillaria meffeu but not with laccase 11. The isolectric pH was 4.1 for laccase I and 3.3 for laccase 11
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