Laccases from Polyporus versicolor

We illustrate these aspects of metalloprotein dynamics at surfaces by two specific proteins. One is the two-centre bacterial di-heme protein cyt c4 from Pseudomonas stutzeri, and the other is the fungal four-centre redox enzyme laccase from Polyporus versicolor. 

Figure 1. Visible CD (A) and absorption spectra (B) of azurin from Pseudomonas aeruginosa (left) and laccase from Polyporus versicolor...

The redox potential of the Tl Cu-site has been determined using potentiometric titrations with redox mediators for a large number of different laccases and varies between 410 mV vs. NHE for Rhus vernicifera [67] and 790 mV for laccases from Polyporus versicolor and Coriolus hirsutus [244,251]. The T2 and T3 sites have higher potentials [251]. 

Extended quinones. A soln. of laccase from Polyporus versicolor added to a soln. of 2-methyl-1-naphthol in 0.01 M acetate buffer of pH 5.4, and kept 4 days at 30° 3,3 -dimethyl-1,1 -binaphthyl-4,4 -quinone. Y 63%. Also with K-ferricyanide, and formation of dinaphthones s. B. R. Brown and A. H. Todd, Soc. 1963, 5564 with K-ferricyanide and lead dioxide s. F. R. Hewgill and B. S. Middleton, Soc. 1965, 2914. 

Laccase from Polyporus versicolor (E.C. 1.10.3.2., 180 000 U/ml) was obtained from the Institute of Biochemistry, Academy of Sciences, Armenian SSR. Peroxidase (POD) from milk (E.C. 1.11.1.7., 340 pmol/l) was a ift from the Institute of Physiological Chemistry, University of Umea (Sweden). Other reagents used were of analytical grade. The background solution was a Sorenson phosphate buffer of pH 5.0 - 7.0 or 0.1 M acetate buffer of pH 5.5. 

Fungal laccase A from Polyporus versicolor, a copper-containing oxidase... 

As with soil, diphenol oxidases extracted from forest litter also can be fractionated to yield components essentially free of co-extracted humic compounds. A comparison of humic-free laccases (p-diphenol oxidases) purified from soil and litter extracts with those from Polyporus versicolor indicated that the former preparations were strongly electronegative and were only weakly adsorbed to humic colloids. By contrast other enzymically-active fractions from soil extracts were associated with humic compounds in complexes which were not separable by chromatography or electrophoresis. ... 

Faced with the problem of elucidating the individual roles of the diflFerent copper centers in the blue oxidases, the researcher has naturally focused in recent years on the laccases (9). Being easier to isolate, better characterized, and containing fewer copper atoms than cemloplasmin or ascorbate oxidase, the laccases from the Japanese lacquer tree Rhus vernicifera and the fungus Polyporus versicolor have been the subject of several transient kinetic studies in the millisecond range, that is, studies using stopped-flow spectrophotometry and rapid-freeze EPR spectroscopy (9,49,50). 

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