Chloroperoxidase-catalyzed benzylic hydroxylation.
Chloroperoxidase-catalyzed benzylic hydroxylation.
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氯过氧化物酶催化的苄基羟基化。
DOI：
10.1006/abbi.1995.1302
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发表时间：
1995
影响因子：
3.9
通讯作者：
OrtizdeMontellano,PR
中科院分区：
文献类型：
--
作者：
Miller,VP;Tschirret-Guth,RA;OrtizdeMontellano,PR
氯过氧化物酶可将对甲基苯甲醚和对乙基苯甲醚分别氧化为4-甲氧基苯甲醇和1-（4′-甲氧基苯基）乙醇。它不能有效地将甲苯氧化成苯甲醇，但似乎不能氧化被强吸电子基团取代的甲苯。还观察到O-去甲基化。该酶对帕拉以外的取代基敏感，并且如果它带有额外的甲基或甲氧基，则不会可检测地催化对甲基苯甲醚的苄基羟基化。一个例外是1，2-（亚甲二氧基）-4-甲基苯，其被氧化为3，4-（亚甲二氧基）苄醇和2-羟基-4-甲基苯酚。用H218 O2进行的研究表明，在对甲基苯甲醚氧化为4-甲氧基苄醇的过程中，所有进入产物中的氧都来自过氧化物。对甲基苯甲醚的单氘代和双氘代甲基类似物被氧化，分别具有3.51和3.34的明显分子内同位素效应。从带有羟基的碳上提取氢与苄基氧化有效地竞争，因为2-[1，1 - 2 H2]苯基乙醇被氧化成2-[1- 2 H]-而不是2-[1，2 - 2 H2]苯乙醛。因此醛的形成涉及甲醇氢的提取，而不是氢迁移到苄型碳阳离子中间体。氯过氧化物酶类似于细胞色素P450，因为它催化苄基羟基化反应，但它具有更有限的底物特异性。
Chloroperoxidase oxidizes p-methylanisole and p-ethylanisole to 4-methoxybenzyl alcohol and 1-(4′-methoxyphenyl)ethanol, respectively. It ineffectively oxidizes toluene to benzyl alcohol but does not appear to oxidize toluene substituted with strong electron-withdrawing groups. O-Demethylation is also observed. The enzyme is sensitive to substituents at other than the para position and does not detectably catalyze benzylic hydroxylation of p-methylanisole if it bears additional methyl or methoxy groups. An exception is 1,2-(methylenedioxy)-4-methylbenzene, which is oxidized to both 3,4-(methylenedioxy)benzyl alcohol and 2-hydroxy-4-methylphenol. Studies with H218O2indicate that all the oxygen incorporated into the product in the oxidation of p-methylanisole to 4-methoxybenzyl alcohol derives from the peroxide. The mono- and dideuterated methyl analogues of p-methylanisole are oxidized with apparent intramolecular isotope effects of 3.51 and 3.34, respectively. Abstraction of a hydrogen from a carbon bearing a hydroxyl group competes effectively with benzylic oxidation because 2-[1,1-2H2]phenylethanol is oxidized to 2-[1-2H]- rather than 2-[1,2-2H2]phenylacetaldehyde. Aldehyde formation therefore involves abstraction of the carbinol hydrogen rather than hydrogen migration to a benzylic carbocation intermediate. Chloroperoxidase resembles cytochrome P450 in that it catalyzes benzylic hydroxylation reactions but it has a more limited substrate specificity.