Laccases: complex architectures for one-electron oxidations.

Laccase (p-diphenol:dioxygen oxidoreductase), one of the earliest discovered enzymes, contains four copper ions in two active sites and catalyzes a one-electron oxidation of substrates such as phenols and their derivatives, or aromatic amines, coupled to a four-electron reduction of dioxygen to water. The catalytic mechanism has been studied for decades but is still not completely elucidated, especially in terms of the reduction of dioxygen to water. The key structural features of this enzyme are under investigation in several groups using techniques such as X-ray diffraction, electron paramagnetic resonance (EPR) spectroscopy, and site-directed mutagenesis. The high interest in laccases is explained by the large number of biotechnological applications. In this review, the most recent research on the overall structural features as well as on the structures and properties of the active sites are summarized, along with currently proposed mechanisms of reaction.

Anti-inflammatory effects of Allium schoenoprasum L. leaves.

Allium schoenoprasum has antimicrobial and antifungal properties and is used to relieve pain from sunburn and sore throat. The aim of the present study was to evaluate the anti-inflammatory effects of the extracts from A. schoenoprasum leaves. A 1:1 (w:v) extract was prepared by a modified Squibb repercolation method. The total phenolic content of 68.5±2 g gallic acid aquivalent (GAE)/g plant was determined using the Folin-Ciocalteu method. The in vitro antioxidant activity was determined using the 1,1-diphenyl-2-picrylhydrazyl bleaching method (6.72±0.44 g/mg DPPH) and the trolox equivalent antioxidant capacity (132.8±23 g trolox eq./g plant) assay. Analysis of the extracts using the hemoglobin ascorbate peroxidase activity inhibition assay or the electron spin resonance did not yield signals above the detection limit. The anti-inflammatory effects of three extract concentrations (25%, 50%, 100%) were evaluated in vivo on a model turpentine oil-induced inflammation in rats. These three extracts were also evaluated in vitro for the ability to inhibit phagocytosis, the accumulation of total nitrites and nitrates in the serum, the total oxidative status, the total antioxidant response and the oxidative stress index. Pure extracts (100% concentration) had the best inhibitory activity on phagocytosis and oxidative stress. In conclusion, these results support the hypothesis that extracts from A. schoenoprasum leaves exert anti-inflammatory activities by inhibiting phagocytosis through the reduction of nitro-oxidative stress.