Search

Biochemical stability of soil humus is an important factor affecting soil quality. Fungi are among the most efficient decomposers of humic matter due to presence of oxidative enzymes, including phenoloxidase laccase. Production of laccase by zygomycetes, a group of cellulolytic fungi widespread in soil, is poorly studied. The potential role of laccase from zygomycetes in humus turnover is unknown. Here, we show for the first time that laccase of zygomycetous fungus Mortierella elasson can effectively depolymerize humic acids in vitro. The fungus produced laccase extracellularly in a liquid culture medium. Unlike in case of laccases in ligninolytic basidiomycetes, attempts to increase enzyme activity using inductors, changes in the source of nitrogen and carbon failed to lead to any increase in laccase production. Laccase was purified using ion exchange chromatography and gel filtration. The molecular weight of the laccase was 51.75 kDa. The laccase catalyzed the oxidation of ABTS and K4[Fe(CN)6], phenolic compounds, but not tyrosine. The laccase activity was inhibited by NaN3 and NaF. The pH optimum of the laccase activity was 3.0 for ABTS and 5.0 for 2,6-dimethoxy phenol. The enzyme had moderate thermal stability and was rapidly inactivated at 70 °C. Purified laccase depolymerized humic acids from retisol, compost and peat more effectively than culture liquid containing laccase. The results of the study extend our knowledge of the role of laccases from different producers in the transformation of natural organic matter.

Various natural and synthetic polyanionic polymers with different chemical structures are known to exhibit potent antiviral activity in vitro toward a variety of enveloped viruses and may be considered as promising therapeutic agents. A water-soluble conjugate of 2,5-dihydroxybezoic acid (2,5-DHBA) with gelatin was synthesized by laccase-catalyzed oxidation of 2,5-DHBA in the presence of gelatin, and its antiviral activity against pseudorabies virus (PRV) and bovine herpesvirus type 1 (BoHV-1), two members of the Alphaherpesvirinae subfamily, was studied. The conjugate produced no direct cytotoxic effect on cells, and did not inhibit cell growth at concentrations up to 1000 µg/mL. It exhibited potent antiviral activity against PRV (IC50, 1.5–15 µg/mL for different virus strains) and BoHV-1 (IC50, 0.5–0.7 µg/mL). When present during virus adsorption, the conjugate strongly inhibited the attachment of PRV and BoHV-1 to cells. The 2,5-DHBA–gelatin conjugate had no direct virucidal effect on the viruses and did not influence their penetration into cells, cell-to-cell spread, production of infectious virus particles in cells, and expression of PRV glycoproteins E and B. The results indicated that the 2,5-DHBA–gelatin conjugate strongly inhibits the adsorption of alphaherpesviruses to cells and can be a promising synthetic polymer for the development of antiviral formulations against alphaherpesvirus infections.