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Spectroscopic studies of the type 2 and type 3 copper centres in the mercury derivative of laccase.

ABSTRACT: U.v.-visible-absorption and e.p.r. spectroscopy were used to study the type 2 and type 3 copper centres in the mercury derivative of laccase. After treatment with peroxide the mercury derivative of laccase exhibits a fully developed absorption band at 330 nm (delta epsilon = 2900 +/- 100 M-1.cm-1, which is characteristic of type 3 copper in the oxidized state. In addition, there is a weak ligand-field absorption at 740 nm (epsilon = 380 +/- 30 M-1.cm-1), which can be assigned to the type 3 pair. Because the e.p.r. spectrum of the type 2 copper is well resolved in the case of the mercury derivative of laccase, for the first time we have been able to observe spectroscopic evidence for a pH-dependent structural transition that has been invoked to explain the kinetics of enzyme reduction [Andréasson & Reinhammar (1979) Biochim. Biophys. Acta 568, 145-156]. According to the e.p.r. data the pKa lies in the range 6-7, and comparisons with a model compound show that the spectral changes can plausibly be interpreted in terms of the deprotonation of a water molecule in the co-ordination sphere of the type 2 copper.

SUBMITTER: Tamilarasan R

PROVIDER: S-EPMC1133446 | biostudies-other | 1989 Oct

REPOSITORIES: biostudies-other

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Project description:Compounds belonging to the group of 5-substituted 4-(1,3,4-thiadiazol-2-yl) benzene-1,3-diols exhibit a broad spectrum of biological activity, including antibacterial, antifungal, and anticancer properties. The mechanism of the antifungal activity of compounds from this group has not been described to date. Among the large group of 5-substituted 4-(1,3,4-thiadiazol-2-yl) benzene-1,3-diol derivatives, the compound 4-(5-methyl-1,3,4-thiadiazole-2-yl) benzene-1,3-diol, abbreviated as C1, was revealed to be one of the most active agents against pathogenic fungi, simultaneously with the lowest toxicity to human cells. The C1 compound is a potent antifungal agent against different Candida species, including isolates resistant to azoles, and molds, with MIC100 values ranging from 8 to 96 ?g/ml. The antifungal activity of the C1 compound involves disruption of the cell wall biogenesis, as evidenced by the inability of cells treated with C1 to maintain their characteristic cell shape, increase in size, form giant cells and flocculate. C1-treated cells were also unable to withstand internal turgor pressure causing protoplast material to leak out, exhibited reduced osmotic resistance and formed buds that were not covered with chitin. Disturbances in the chitin septum in the neck region of budding cells was observed, as well as an uneven distribution of chitin and ?(1?3) glucan, and increased sensitivity to substances interacting with wall polymerization. The ATR-FTIR spectral shifts in cell walls extracted from C. albicans cells treated with the C1 compound suggested weakened interactions between the molecules of ?(1?3) glucans and ?(1?6) glucans, which may be the cause of impaired cell wall integrity. Significant spectral changes in the C1-treated cells were also observed in bands characteristic for chitin. The C1 compound did not affect the ergosterol content in Candida cells. Given the low cytotoxicity of the C1 compound to normal human dermal fibroblasts (NHDF), it is possible to use this compound as a therapeutic agent in the treatment of surface and gastrointestinal tract mycoses.

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Spectroscopic studies of the type 2 and type 3 copper centres in the mercury derivative of laccase.

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