Purification and characterization of an extracellular laccase of a fungus (family Chaetomiaceae) isolated from soil

• Published in: Enzyme and microbial technology Vol. 33; no. 4; pp. 520 - 526
• Main Authors: Saito, Takao, Hong, Peng, Kato, Katsuya, Okazaki, Masaharu, Inagaki, Hidetoshi, Maeda, Sumio, Yokogawa, Yoshiyuki
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Amsterdam Elsevier Inc 01.09.2003; Elsevier Science
• Subjects: 2,6-dimethoxyphenol; Biodegradation; Biological and medical sciences; Biology of microorganisms of confirmed or potential industrial interest; Biotechnology; Bisphenol A; Botryotinia fuckeliana; Chaetomiaceae; Characterization; coumaric acid; cysteine; dithiothreitol; Fundamental and applied biological sciences. Psychology; Fungi; Isolation; kojic acid; Laccase; Miscellaneous; Mission oriented research; Nonylphenol; Purification; thioglycolic acid; Fungi; Characterization; Biodegradation; Bisphenol A; Purification; Isolation; Nonylphenol; Laccase; Enzyme; Extracellular; Soils; Oxidoreductases; Thallophyta
• ISSN: 0141-0229; 1879-0909
• DOI: 10.1016/S0141-0229(03)00158-3

A laccase-producing fungus was newly isolated from soil and shown to belong to family Chaetomiaceae. The extracellular laccase was purified to electrophoretic homogeneity from coffeic acid-induced culture medium by ammonium sulfate precipitation and anion exchange column chromatography. The enzyme was determined to be a monomeric protein with an apparent molecular mass of approximately 73–80 kDa and an isoelectric point (p I) of 3.5. One of its peptide fragments derived by endopeptidase digestion had a 68.75% amino acid sequence homologous to that of laccase I of Botryotinia fuckeliana. Spectroscopic analysis revealed that the enzyme has four bound copper atoms, a type I Cu(II), a type II Cu(II), and a type III binuclear Cu(II). The optimum pH for the oxidation of syringaldazine was 7.0 and the optimum temperature was 42 °C. The laccase was stable for up to 288 h at 4 °C and its respective half-life times at 25 and 40 °C were estimated to be 150 and 20 h. The enzyme reaction was inhibited by l-cysteine, dithiothreitol (DTT), p-coumaric acid, kojic acid, and thioglycolic acid. The enzyme oxidized various known laccase substrates, its lowest K m value being for syringaldazine, highest k cat value for 4-hydroxyindole, and highest k cat/ K m for 2,6-dimethoxy-phenol. In addition to these substrates, this laccase was effective for the biodegradation of endocrine-disrupting chemicals such as bisphenol A and nonylphenol (NP).