Redox silencing of the Fenton reaction system by an alkylitaconic acid, ceriporic acid B produced by a selective lignin-degrading fungus, Ceriporiopsis subvermispora
作者:Yasunori Ohashi、Yoshihiko Kan、Takahito Watanabe、Yoichi Honda、Takashi Watanabe
DOI:10.1039/b614379b
日期:——
The selective lignin-degrading fungus, Ceriporiopsis subvermispora secretes alkylitaconic acids (ceriporic acids) during wood decay. We reported that ceriporic acid B (hexadecylitaconic acid) was protective against the depolymerization of cellulose by the Fenton reaction. To understand the redox silencing effects, we analyzed the physicochemical and redox properties of itaconic, octylitaconic and hexadecylitaconic acids. The initial rate of HO˙ production by the Fenton system with Fe3+, H2O2 and L-cysteine was suppressed by hexadecylitaconic and octylitaconic acids by 0.04 and 0.16 of the reaction rate without chelators. ESR, O2 uptake and the assay of Fe2+ with BPS demonstrated that Fe3+ reduction by L-cysteine was suppressed by hexadecylitaconic and octylitaconic acids while the reaction of Fe2+ with H2O2 was not suppressed by the two alkylitaconic acids. Ligand exchange experiments with NTA demonstrated that Fe3+ chelation by two carboxyl groups of alkylitaconic acids is a critical step in iron redox modulation. In stark contrast, the production of HO˙ and reduction of Fe3+ were not suppressed by itaconic acid due to HO˙-initiated degradation of the chelator. The strong redox silencing effects by a series of alkylitaconic acids have attracted interest in controlling microbial plant cell wall degradation and chemoprotection against cellular oxidative injury.
选择性木质素降解真菌 Ceriporiopsis subvermispora 在木材腐烂过程中会分泌烷基硝酸(ceriporic acids)。我们曾报道过塞里硼酸 B(十六烷基硝酸)对芬顿反应中纤维素的解聚具有保护作用。为了了解氧化还原沉默效应,我们分析了衣康酸、辛基硝酸和十六烷基硝酸的物理化学和氧化还原特性。在含有 Fe3+、H2O2 和 L-半胱氨酸的 Fenton 系统中,十六烷基二十二酸和辛基二十二酸抑制了 HO˙产生的初始速率,分别为不含螯合剂时的 0.04 和 0.16。ESR、O2 摄取和用 BPS 对 Fe2+ 进行的检测表明,十六烷基二十二酸和辛基二十二酸抑制了 L-半胱氨酸对 Fe3+ 的还原,而这两种烷基二十二酸并不抑制 Fe2+ 与 H2O2 的反应。用 NTA 进行的配体交换实验表明,Fe3+ 与烷基二十二酸的两个羧基螯合是铁氧化还原调节的关键步骤。与此形成鲜明对比的是,由于 HO˙引发的螯合剂降解,衣康酸并没有抑制 HO˙的产生和 Fe3+ 的还原。一系列烷基衣康酸的强氧化还原沉默效应引起了人们对控制微生物植物细胞壁降解和细胞氧化损伤化学保护的兴趣。