Effect of Mn(II) on reactions catalyzed by lignin peroxidase from Phanerochaete chrysosporium

Abstract

The effect of manganese on lignin peroxidase activity was studied. The enzyme was produced with a new process using an air-lift-type reactor. The experiments were performed with veratryl alcohol and a dimeric lignin model compound. It was shown that when Mn(I1) . lactate complex was present the amount of veratraldehyde formed and the uptake of oxygen were significantly enhanced during the aerobic oxidation of veratryl alcohol. A similar effect can be obtained with superoxide dismutase. These results strongly suggest that the superoxide anion can occur during the reaction; its scavenging by Mn(I1) or superoxide dismutase generates H202. In contrast, no evidence for the formation of superoxide anion was found during oxidation of the lignin model, compound veratrylglycerol-/3-guaiacyl ether.The discovery of the extracellular ligninolytic system of the white-rot fungus Phanerochaete chrysosporium [1, 21 has renewed interest in biodelignification. The constituents of this system have been identified as two types of peroxidase, now referred to as lignin peroxidase or ligninase, and manganesedependent peroxidase. Recently, Kersten et al. [3] demonstrated an H202-generating system, a glyoxal oxidase in ligninolytic cultures.Lignin peroxidase is able to catalyse a variety of reactions in lignin model compounds. This enzyme functions by singleelectron oxidation, leading to cation radical intermediates [4, 51; their further decomposition and the evolution of the radical-moiety depend on their chemical structure [6 -91. Such a mechanism could explain the non-specificity of lignin-peroxidase-catalyzed reactions, and makes this enzyme important for lignin depolymerisation.The activity of manganese-dependent peroxidase toward phenolic substrates depends on the presence of manganese [lo, 111. This peroxidase oxidizes Mn(I1) to Mn(III), which is in fact the effective oxidative agent involved in the enzymic reactions [12].As lignin is a complex polymer, its biodegradation may require some synergy between enzymes. In this paper, we examine if manganese also has an effect on lignin peroxidase activity. For this purpose, lignin peroxidase was isolated from the culture fluid of P. chrysosporium grown in an air-lift-type reactor, with a glycerol/high-nitrogen-supplemented medium. The experiments were performed with two substrates, veratryl alcohol, a secondary metabolite produced by the fungus during lignin biodegradation [13], and veratrylglycerol-P-guaiacyl ether, a dimeric lignin model compound.

Participation of Mn(II) in the catalysis of laccase, manganese peroxidase and lignin peroxidase from Phlebia radiata

“…Our results conflict with previous data reported for LiP under corresponding experimental conditions [ 171, i.e. using lactic acid as a chelator for manganese ions, which showed that addition of 0.1 mM Mn(I1) significantly increased the amount of veratraldehyde formed both at pH 3.0 and 4.5 It was proposed [17] that the observed increase was due to the scavenging of superoxide anions by Mn(I1) lactate, which would then generate HZO, thereby leading to an overproduction of veratraldehyde by LiP [17].…”

On a revised mechanism of side product formation in the lignin peroxidase catalyzed oxidation of veratryl alcohol

“…If this were true then the intermediate radical products would still be available for subsequent reactions that do lead to other side products than those that were identified. However, no other products have been detected in the presence of Mn 2+ [16]. Thus, the role of Mn 2+ in VA side product formation needs reexamination too.…”

Lignolytic Enzymes of a MushroomStereum ostreaIsolated from Wood Logs

“…Growth of P. chrysosporium in submerged fermentation generated MnP and LiP with specific activity of 144 and 14 U/mg, respectively [26]. Yields of lignolytic peroxidase enzymes in majority of studies with different strains of P. chrysosporium in liquid medium occurred within a range of 0.07–0.8 U/mL [12, 27–30]. Growth of other organisms— Trametes versicolor [23, 31], hyperlignolytic fungus IZU-154 [32], the strain K 1 isolated from polyphenol polluted site [33], Nematoloma forwardii [34], and Pleurotus pulmonarius [35] in solid state fermentation/submerged fermentation produced lignolytic peroxidases at low levels.…”

“…Profiles of enzymes of lignolytic system depend on growth conditions and vary from one organism to another. Peroxidases are dominant in lignolytic system in respect of P. chrysosporium, where laccase is a major component in lignolytic system of Ganoderma adspersum [6, 12, 13]. In view of broader specificity and oxidation of wider range of xenobiotic compounds including chlorinated phenolics, synthetic dyes, pesticides, and polycyclic aromatic hydrocarbons, lignolytic enzymes offer advantages for biotechnological applications.…”