Impact of sulfur-compounds on lignin peroxidase activity from Penicillium chrysogenum

Background: The objective of this study was to evaluate the effects of different sulfur-containing compounds, including N-acetyl cysteine (NAC), cysteine, thioglycolate, and glutathione (GSH) on the activity of lignin peroxidase (LiP, EC 1.11.1.14) from Penicillium chrysogenum. Methods: The enzyme was isolated and purified through a three-step procedure involving 80% ammonium sulphate precipitation, DEAE-Sepharose ion-exchange chromatography, and Sephadex G-200 gel filtration. The activity of the purified enzyme was evaluated in the presence of cysteine, N-acetylcysteine (NAC), thioglycolate, and reduced glutathione (GSH) at various concentrations (50, 75, 100, 125, 150, and 175 μmol). Results: Sulfur compounds enhanced the enzyme activity at the lower concentrations but they were inhibitors at the higher levels. These findings are noteworthy, suggesting that the strategic use of such compounds could help to sustain LiP activity for industrial applications. Conclusion: Thiol compounds may activate lignin peroxidase (LiP) at low concentrations by protecting its sulfhydryl groups and decreasing Km enhancing activity. However, at higher concentrations, they may inhibit the enzyme by interfering with enzyme-substrate complex formation, reducing overall catalytic efficiency.