Chung N, Aust S D
Biotechnology Center, Utah State University, Logan 84322-4705.
Arch Biochem Biophys. 1995 Feb 1;316(2):733-7. doi: 10.1006/abbi.1995.1097.
Veratryl alcohol (VA) oxidation by lignin peroxidase (LiP) was inhibited by phenol. The enzyme was quickly converted to compound III, an inactive intermediate. However, as soon as VA began to be oxidized, compound II was observed. The lag period before VA oxidation was affected by the concentrations of both phenol and VA. The addition of VA increased the extent of phenol oxidation and the kinetics of phenol oxidation in the presence of VA were similar to those of VA oxidation. Previously it was shown that the VA cation radical (VA.+) was responsible for the conversion of compound III back to ferric enzyme [D. P. Barr and S. D. Aust (1994) Arch. Biochem. Biophys. 312, 511-515]. Here we observed that the reversion of compound III to active ferric enzyme in the presence of VA was prevented by addition of phenol, suggesting that VA.+ oxidizes phenol to phenoxyl radical. This hypothesis was also supported by the observation that O2 consumption during VA oxidation was inhibited by the addition of phenol. All of these results suggested that VA was first oxidized by LiP to VA.+ and then it oxidized phenol to phenoxyl radical while VA.+ was reduced back to VA. Activity was lost as compound III accumulated since the VA.+ was consumed by the oxidation of phenol. After all of the phenol was oxidized, VA.+ became available to convert compound III back to ferric enzyme.
藜芦醇（VA）被木质素过氧化物酶（LiP）氧化的过程受到苯酚的抑制。该酶会迅速转化为化合物III，一种无活性的中间体。然而，一旦VA开始被氧化，就会观察到化合物II。VA氧化之前的延迟期受到苯酚和VA浓度的影响。VA的添加增加了苯酚氧化的程度，并且在有VA存在的情况下苯酚氧化的动力学与VA氧化的动力学相似。先前的研究表明，VA阳离子自由基（VA.+）负责将化合物III转化回铁酶[D.P.巴尔和S.D.奥斯特（1994年）《生物化学与生物物理学档案》312卷，第511 - 515页]。在这里我们观察到，在有VA存在的情况下，加入苯酚会阻止化合物III转化为活性铁酶，这表明VA.+将苯酚氧化为苯氧基自由基。这一假设还得到了以下观察结果的支持：在VA氧化过程中加入苯酚会抑制氧气的消耗。所有这些结果表明，VA首先被LiP氧化为VA.+，然后它将苯酚氧化为苯氧基自由基，同时VA.+被还原回VA。由于VA.+被苯酚的氧化所消耗，随着化合物III的积累，活性丧失。当所有的苯酚都被氧化后，VA.+可用于将化合物III转化回铁酶。
