Effect of Low Doses of Guaiacol and Ethanol on Enzymatic Activity of Fungal Cultures

The influence of low doses of guaiacol and ethanol, the natural effectors of lignin and phenolics transformations, on laccase and peroxidase activities produced by two strains of Basidiomycetes, Pleurotus sajor-caju and Trametes versicolor, was evaluated. Fungal mycelia were grown for 2 weeks on liquid media containing serial dilutions of guaiacol or ethanol ranging from 100−1 to 100−20 mol/L. Laccase and peroxidase activities in the medium were measured at the end of 2 weeks. The effect of low doses of guaiacol and ethanol on enzyme activities was manifested in an oscillating manner. Similar response patterns were observed when pure enzymes were exposed to the same serial dilutions of guaiacol and ethanol. T. versicolor cultures enriched with 40 mmol guaiacol (simulating natural environmental conditions) also displayed oscillating enzyme activity patterns in response to serial dilutions of guaiacol, but the maximum enzyme activity values were increased compared to those observed in cultures not receiving 40 mmol guaiacol. The differences between maxima and minima varied among the experimental groups and depended on the species of fungus, type of effector, and kind of enzyme. The results suggests the possibility of subtle regulation of enzymatic activity on the molecular level

The Influence of Very Low Doses of Cisplatin on Tumor Cell Proliferation In Vitro and on Some Hematological and Enzymatic Parameters of Healthy Rats

Healthy rats had been treated for 2 or 6 weeks with 1.0 mL of 10-8 and 10-16 mg/mL of cisplatin. After 2 weeks of treatment, a significant increase in leukocyte and erythrocyte count and also in hematocrit was observed. Among leukocytes the number of neutrophils and eosinophils significantly increased. Biochemical analyses indicated a decrease in the glycogen content in the liver and kidneys after 2 weeks of treatment with low doses of cisplatin but at the end of the experiment (8th week of experiment) the stores of glycogen increased significantly. Biochemical analyses concerning the activity of some enzymes in the liver revealed a significant increase of peroxidase and acid phosphatase as well as catalase activities after 2 weeks of treatment. However, catalase was induced by a very low concentration of cisplatin, 10-16 mg/mL. After the cessation of cisplatin treatment the activity of enzymes returned to normal values. Human lung carcinoma cell line A549 (ECACC No 86012804) was also studied after treatment with the same doses of cisplatin and inhibition of its growth was observed. The results of these experiments strongly indicated that low doses of cisplatin could be stimulating for healthy cells but cytostatic for tumor cells. Possible mechanisms involved in the biological activity of very low cisplatin concentrations are discussed

Influence of very low doses of mediators on fungal laccase activity - nonlinearity beyond imagination

Laccase, an enzyme responsible for aerobic transformations of natural phenolics, in industrial applications requires the presence of low-molecular substances known as mediators, which accelerate oxidation processes. However, the use of mediators is limited by their toxicity and the high costs of exploitation. The activation of extracellular laccase in growing fungal culture with highly diluted mediators, ABTS and HBT is described. Two high laccase-producing fungal strains, Trametes versicolor and Cerrena unicolor, were used in this study as a source of enzyme. Selected dilutions of the mediators significantly increased the activity of extracellular laccase during 14 days of cultivation what was distinctly visible in PAGE technique and in colorimetric tests. The same mediator dilutions increased demethylation properties of laccase, which was demonstrated during incubation of enzyme with veratric acid. It was established that the activation effect was assigned to specific dilutions of mediators. Our dose-response dilution process smoothly passes into the range of action of homeopathic dilutions and is of interest for homeopaths

Amperometric detection of mono- and diphenols at Cerrena unicolor laccase-modified graphite electrode: correlation between sensitivity and substrate structure

Graphite electrode modified with laccase from Cerrena unicolor served as a biosensor for detection of 30 phenolic compounds with different structures. Some correlations of the sensor response to the structures of substrates are discussed. This biosensor responded to: (i) nanomolar concentrations of some of the selected phenolic compounds, e.g., 2,6-dimethoxyphenol,coniferyl alcohol, caffeic acid, DOPAC and hydroquinone, (ii) micromolar concentrations, e.g., ferulic acid, syringic acid, dopamine, 3,4-dihydroxybenzoic acid and DL-noradrenaline, and (iii) millimolar concentrations in the case of phenol and 4-hydroxybenzaldehyde. Among the ortho- or para-substituted phenols, the sensitivity of the C unicolor laccase-modified electrode increased in the following order -H, -CH3, -OH, -OCH3 and -NH3+ but in the case of para-substituted phenols, the K-m(app) values were lower. The sensitivity of the laccase electrode increased with an additional -OH group in para-substituted phenols. In the case of the selected compounds, kinetic data from electrochemical flow injection system were compared with those obtained from experiments in solution. (c) 2005 Elsevier B.V. All rights reserved

Use of laccase-modified electrode for amperometric detection of plant flavonoids

In this study, laccase from Cerrena unicolor as a highly active enzyme was adsorptively immobilized on the surface of graphite electrode. The electrode inserted into flow-injection system served as a biosensor for detection of polyphenols, including flavonoids. We used catechin hydrate, epicatechin, epicatechin gallate, prodelphinidin, and caffeic acid as a target compounds in determination. The performed investigations demonstrate that laccase from white rot fungus C unicolor can be applied for the construction of biosensors useful for determination of flavonoids and related compounds in flow-injection system. Electrodes modified with laccase yield responses for both simple compounds (caffeic acid) and compounds with three or more phenolic and non-phenolic rings, although with different sensitivity. (C) 2004 Elsevier Inc. All rights reserved