Lignin peroxidase oxidation of Mn2+ in the presence of veratryl alcohol, malonic or oxalic acid, and oxygen.
Lignin peroxidase oxidation of Mn2+ in the presence of veratryl alcohol, malonic or oxalic acid, and oxygen.
复制标题
在藜芦醇、丙二酸或草酸以及氧气存在下，木质素过氧化物酶氧化 Mn2。
DOI：
10.1021/bi00498a008
复制
发表时间：
1990
期刊：
影响因子：
2.9
通讯作者：
Kirk,TK
中科院分区：
文献类型：
--
作者：
Popp,JL;Kalyanaraman,B;Kirk,TK
摘要：Veratryl醇（3,4 -二甲氧基苯甲醇）在黄孢Phanerochaete chrysosporium降解木质素中似乎具有多种作用。它是由真菌合成的。它能诱导木质素过氧化物酶（LiP）的表达，并对H202对LiP的失活具有保护作用。此外，戊曲醇已被证明可以增强对不是良好的LiP底物的化合物的LiP氧化。我们现在已经观察到在含有LiP、Mn2+、戊戊醇、丙二酸缓冲液、H202和02的反应混合物中Mn3+的形成。若不加入戊醇和H202，则不生成Mn3+。Mn3+的形成也表现出对氧气的绝对需求，并且在反应中观察到氧气的消耗。这表明活性氧参与其中。在实验中使用草酸盐（P. chrysosporium的代谢物）代替丙二酸盐，获得了类似的结果。然而，在这种情况下，我们检测到（通过ESR自旋捕获）二氧化碳阴离子自由基（co2 *~）和过羟基自由基（）在含有LiP、草酸盐、戊四醇、H202和02的反应混合物中的产生。我们的数据表明草酸自由基的形成，它衰变为co2和co2 ' "。后者与02反应生成02*~，然后将Mn2+氧化为Mn3+。在不含戊曲醇的情况下未检测到自由基。这些结果表明，LiP可以间接氧化Mn2+，戊戊醇可能是该体系中的自由基介质。与担子菌真菌黄孢Phanerochaete chrysosporium降解木质素相关的胞外酶有木质素过氧化物酶（LiP）、1锰过氧化物酶（MnP）和生成h2的乙二醛氧化酶（Kirk & Farrell, 1987）。LiP将木质素的芳香核氧化为非酶反应的阳离子自由基，导致脂肪侧链和芳香核的分裂。与LiP相关的MnP将Mn2+氧化为Mn3+。Mn3+可以氧化木质素的酚类单位，也被认为参与木质素的断裂（Wariishi等，1989）。除了这些酶外，一种芳香代谢物3,4 -二甲氧基苄基（戊曲霉）醇，似乎是P. chrysosporium木质素分解系统的一个组成部分。戊曲醇在木质素的生物降解过程中具有多种作用。它刺激LiP的产生（Faison & Kirk, 1985），并保护LiP免受H202的失活（Tonon & Odier, 1988）。也有研究表明，它可以增强对不是好的LiP底物的化合物的LiP氧化（Harvey et al., 1986）。我们现在已经发现，lip在戊四醇、丙二酸或草酸存在下，氧将Mn2+氧化成Mn3+。这些结果提供了进一步的证据，戊曲醇部分功能作为电子转移剂或介质的氧化非lip底物。由于草酸盐是P. chrysosporium的正常代谢物，LiP可能像MnP一样在生理条件下氧化mn2 +。实验程序
Revised Manuscript Received August 27, 1990 abstract: Veratryl alcohol (3, 4-dimethoxybenzyl alcohol) appears to have multiple roles in lignin degradation by Phanerochaete chrysosporium. It is synthesized de novo by the fungus. It apparently induces expression of lignin peroxidase (LiP), and it protects LiP from inactivation by H202. In addition, veratryl alcohol has been shownto potentiate LiP oxidation of compounds that are not good LiP substrates. We have now observed the formation of Mn3+ in reaction mixtures containing LiP, Mn2+, veratryl alcohol, malonate buffer, H202, and 02. No Mn3+ was formed if veratryl alcohol or H202 was omitted. Mn3+ formation also showed an absolute requirementfor oxygen, and oxygen consumption was observed in the reactions. This suggests involvement of active oxygen species. In experiments using oxalate (a metabolite of P. chrysosporium) instead of malonate, similar results were obtained. However, in this case, we detected (by ESR spin-trapping) the production of carbon dioxide anion radical (C02*~) and perhydroxyl radical () in reaction mixtures containing LiP, oxalate, veratryl alcohol, H202, and 02. Our data indicate the formation of oxalate radical, which decays to C02 and C02 ‘“. The latter reacts with 02 to form 02*~, which then oxidizes Mn2+ to Mn3+. No radicals were detected in the absence of veratryl alcohol. These results indicate that LiP can indirectly oxidize Mn2+ and that veratryl alcohol is probably a radical mediator in thissystem. tjfxtracellular enzymes associated with lignin degradation by the basidiomycetous fungus Phanerochaete chrysosporium are lignin peroxidase (LiP), 1 manganese peroxidase (MnP), and the H202-generating enzyme glyoxal oxidase (Kirk & Farrell, 1987). LiP oxidizes aromatic nuclei of lignin to cation radicals that react nonenzymatically, resulting incleavages in both the aliphatic side chains and the aromatic nuclei. MnP, related to LiP, oxidizes Mn2+ to Mn3+. Mn3+ can oxidize phenolic units of lignin and has been suggested also to be involved in lignin fragmentation (Wariishi et al., 1989). In addition to these enzymes, an aromatic metabolite, 3, 4-dimethoxybenzyl (veratryl) alcohol, seems to be a component of the ligninolytic system of P. chrysosporium. Veratryl alcohol apparently has multiple roles in lignin biodegradation. It stimulates production of LiP (Faison & Kirk, 1985), and it protects LiP from inactivation by H202 (Tonon & Odier, 1988). It also has been shown to potentiate LiP oxidation of compounds that are not good LiP substrates (Harvey et al., 1986).We have now found thatLiP in the presence of veratryl alcohol, malonic or oxalic acid, and oxygen oxidizes Mn2+ to Mn3+. These results provide further evidence that veratryl alcohol functions in part as an electron transfer agent or mediator of oxidations of non-LiP substrates. Because oxalate is a normal metabolite of P. chrysosporium, it is possible that LiP, like MnP, oxidizesMn2+ under physiological conditions. Experimental Procedures