Collins P J, Field J A, Teunissen P, Dobson A D
Microbiology Department, University College, Cork, Ireland.
Appl Environ Microbiol. 1997 Jul;63(7):2543-8. doi: 10.1128/aem.63.7.2543-2548.1997.
Supplementation of various cultures of white rot fungi with tryptophan was found to have a large stimulatory effect on lignin peroxidase activity levels. This enhancement was greater than that observed in the presence of the lignin peroxidase recycling agent veratryl alcohol. Using reverse transcription-PCR, we found that tryptophan does not act to induce lignin peroxidase expression at the level of gene transcription. Instead, the activity enhancement observed is likely to result from the protective effect of tryptophan against H2O2 inactivation. In experiments using a partially purified lignin peroxidase preparation, tryptophan and its derivative indole were determined to function in the same way as veratryl alcohol in converting compound II, an oxidized form of lignin peroxidase, to ferric enzyme, thereby completing the catalytic cycle. Furthermore, tryptophan was found to be a better substrate for lignin peroxidase than veratryl alcohol. Inclusion of either tryptophan or indole enhanced the oxidation of the azo dyes methyl orange and Eriochrome blue black. Stimulation of azo dye oxidations by veratryl alcohol has previously been shown to be due to its enzyme recycling function. Our data allow us to propose that tryptophan stabilizes lignin peroxidase by acting as a reductant for the enzyme.
研究发现，向各种白腐真菌培养物中添加色氨酸对木质素过氧化物酶的活性水平具有很大的刺激作用。这种增强作用比在存在木质素过氧化物酶循环剂藜芦醇的情况下观察到的增强作用更大。使用逆转录聚合酶链反应，我们发现色氨酸在基因转录水平上不会诱导木质素过氧化物酶的表达。相反，观察到的活性增强可能是由于色氨酸对过氧化氢失活的保护作用。在使用部分纯化的木质素过氧化物酶制剂的实验中，确定色氨酸及其衍生物吲哚在将木质素过氧化物酶的氧化形式化合物II转化为铁酶方面与藜芦醇的作用方式相同，从而完成催化循环。此外，发现色氨酸是木质素过氧化物酶比藜芦醇更好的底物。添加色氨酸或吲哚均可增强偶氮染料甲基橙和铬蓝黑的氧化。先前已证明藜芦醇对偶氮染料氧化的刺激作用是由于其酶循环功能。我们的数据使我们能够提出，色氨酸通过作为该酶的还原剂来稳定木质素过氧化物酶。
