Formation of acyl radical in lipid peroxidation of linoleic acid by manganese‐dependent peroxidase from Ceriporiopsis subvermispora and Bjerkandera adusta

Abstract

Lipid peroxidation by managanese peroxidase (MnP) is reported to decompose recalcitrant polycyclic aromatic hydrocabon (PAH) and nonphenolic lignin models. To elucidate the oxidative process, linoleic acid and 13(S)-hydroperoxy-9Z,11E-octadecadienoic acid [13(S)-HPODE] were reacted with MnPs from Ceriporiopsis subvermispora and Bjerkandera adusta and the free radicals produced were analyzed by ESR. When the MnPs were reacted with 13(S)-HPODE in the presence of Mn(II), H 2 O 2 and tert-nitrosobutane (t-NB), the ESR spectrum contained a sharp triplet of acyl radical (a N 0.81 mT). Formation of acyl radical was also observed in the reactions of Mn(III)-tartrate with 13(S)-HPODE and with linoleic acid, but the latter reaction occurred explosively after an induction period of around 30 min. Reactions of MnP with linoleic acid in the presence of Mn(II), H 2 O 2 and t-NB gave no spin adducts while addition of t-NB after preincubation of linoleic acid with MnP/Mn(II)/H 2 O 2 for 2 h gave spin adducts of carbon-centered (a N 1.53 mT, a H 0.21 mT) and acyl (a N 0.81 mT) radicals. In contrast to linoleic acid, methyl linoleate and oleic acid were not peroxidized by MnP and chelated Mn(III) within a few hours, indicating that structures containing both the 1,4-pentadienyl moiety and a free carboxyl group are necessary for inducing the peroxidation in a short reaction time. These results indicate that MnP-dependent lipid peroxidation is not initiated by direct abstraction of hydrogen from the bis-allylic position during turnover but proceeds by a Mn(III)-dependent hydrogen abstraction from enols and subsequent propagation reactions involving the formation of acyl radical from lipid hydroperoxide. This finding expands the role of chelated Mn(III) from a phenol oxidant to a strong generator of free radicals from lipids and lipid hydroperoxides in lignin biodegradation.

Regulation of Gene Expression during the Onset of Ligninolytic Oxidation by Phanerochaete chrysosporium on Spruce Wood

“…In addition, enzymes involved in the biosynthesis of linoleic acid, the major membrane fatty acid in P. chrysosporium and other white rot basidiomycetes (35), are potentially relevant, because linoleic acid and other unsaturated lipids are oxidized by MnPs in vitro to produce ligninolytic oxidants (8,(36)(37)(38). Some transcripts encoding ⌬ 9 fatty acid desaturases were moderately more abundant at 96 h, notably Phach ID 1783939 (see Table S1 in the supplemental material).…”

Oxidation of a non-phenolic lignin model compound by two Irpex lacteus manganese peroxidases: evidence for implication of carboxylate and radicals

“…The chelated Mn 3+ ions can also react with a certain co-oxidant (or mediator) to generate reactive radicals that can depolymerize the high redox potential non-phenolic lignin. Unsaturated fatty acids (UFA) and their lipid derivatives are such mediators that can be peroxidized to form highly reactive acyl and fatty acid peroxyl radicals acting on the non-phenolic lignin [7–11]. Other mediators such as glutathione (GSH) may also be involved in the formation of thiyl radicals, which are thought to be also involved in the degradation of recalcitrant compounds [12, 13].…”

Phenolic mediators enhance the manganese peroxidase catalyzed oxidation of recalcitrant lignin model compounds and synthetic lignin

“…The reactions were initiated without addition of hydro-634 gen peroxide into the system. According to Watanabe et al (2000) 635 the system involving MnP-dependent lipid peroxidation is an auto-636 oxidative self-propargating system where the peroxides are pro-637 posed to be produced according to Scheme 1. In the initiation step, (Watanabe et al, 2000).…”

“…According to Watanabe et al (2000) 635 the system involving MnP-dependent lipid peroxidation is an auto-636 oxidative self-propargating system where the peroxides are pro-637 posed to be produced according to Scheme 1. In the initiation step, (Watanabe et al, 2000). 656 The lipid peroxidation system was investigated following the 657 oxidation of veratryl alcohol and adlerol by the lipid system (Table 658 3).…”