STIMULATION OF MN-PEROXIDASE ACTIVITY - A POSSIBLE ROLE FOR OXALATE IN LIGNIN BIODEGRADATION
STIMULATION OF MN-PEROXIDASE ACTIVITY - A POSSIBLE ROLE FOR OXALATE IN LIGNIN BIODEGRADATION
复制标题
DOI：
10.1073/pnas.90.4.1242
复制
发表时间：
1993-02-15
影响因子：
11.1
通讯作者：
TIEN, M
中科院分区：
文献类型：
--
作者：
KUAN, IC;TIEN, M
草酸盐是由许多木材降解真菌产生的。我们的研究表明，白腐真菌 Phanerochaete chrysosporium 在诱导木质素分解系统合成的条件下产生细胞外草酸盐。在高营养氮或碳下生长的培养物中检测到很少或没有检测到草酸盐。该细胞外草酸盐通过 HPLC 进行鉴定和定量。草酸氧化酶的分解进一步证实了其身份。细胞外液的草酸盐含量（峰值为 60 μM）与木质素降解酶 Mn 过氧化物酶的细胞外活性平行。值得注意的是，我们证明了草酸盐在生理浓度下可显着刺激锰过氧化物酶催化的酚红氧化，这可能是由于其螯合锰的能力。停流研究还表明，草酸盐加速了锰过氧化物酶的周转。此外，我们发现，在没有外源 H2O2 和分子氧存在的情况下，草酸盐可以支持 Mn 过氧化物酶催化的氧化反应。这些结果使我们能够提出草酸盐（一种由木材破坏真菌产生的普遍存在的化合物）在木质素生物降解中的重要作用。
Oxalate is produced by numerous wood-degrading fungi. Our studies here show that the white-rot fungus Phanerochaete chrysosporium produces extracellular oxalate under conditions that induce synthesis of the ligninolytic system. Little or no oxalate was detected in cultures grown under high nutrient nitrogen or carbon. This extracellular oxalate was identified and quantitated by HPLC. Its identity was further substantiated by its decomposition by the enzyme oxalate oxidase. The oxalate content of the extracellular fluid (peaking at 60 muM) paralleled the extracellular activity of the lignin-degrading enzyme, Mn peroxidase. Significantly, we demonstrated that oxalate, at physiological concentrations, substantially stimulated Mn peroxidase-catalyzed phenol red oxidation, presumably by its ability to chelate Mn. Stopped flow studies also indicate that oxalate accelerates the turnover of Mn peroxidase. Furthermore, we discovered that oxalate can support Mn peroxidase-catalyzed oxidations in the absence of exogenous H2O2 and in the presence of dioxygen. These results allow us to propose an important role for oxalate, a ubiquitous compound produced by wood-destroying fungi, in lignin biodegradation.