Tyrosinase reactivity in a model complex: An alternative hydroxylation mechanism
Tyrosinase reactivity in a model complex: An alternative hydroxylation mechanism
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DOI：
10.1126/science.1112081
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发表时间：
2005-06-24
期刊：
影响因子：
56.9
通讯作者：
Stack, TDP
中科院分区：
文献类型：
--
作者：
Mirica, LM;Vance, M;Stack, TDP
双核铜酶酪氨酸酶激活 O-2 形成 mu-eta(2):eta(2)-过氧二铜 (II) 复合物，将酚类氧化为儿茶酚。据报道，合成的 mu-eta(2):eta(2)-过氧化二铜 (II) 络合物的吸收光谱与酶活性氧化剂的吸收光谱相似，可在 -80 摄氏度下快速羟基化酚盐。在溶液中的极端温度（-120 摄氏度）下添加酚盐后，观察到与双-mu-氧化二铜 (III) 酚盐络合物一致的反应中间体，其中 O-O 键完全断裂。实验性地。随后的羟基化步骤具有亲电芳香族取代机制的特征，类似于酪氨酸酶。总体而言，该合成复合物中连续 O-O 键断裂和 C-O 键形成的证据表明，对于酪氨酸酶进行的苯酚羟基化反应普遍接受的协同或后期 O-O 键断裂有一种替代的密切机制。
The binuclear copper enzyme tyrosinase activates O-2 to form a mu-eta(2):eta(2)-peroxodicopper(II) complex, which oxidizes phenols to catechols. Here, a synthetic mu-eta(2):eta(2)-peroxodicopper(II) complex, with an absorption spectrum similar to that of the enzymatic active oxidant, is reported to rapidly hydroxylate phenolates at -80 degrees C. Upon phenolate addition at extreme temperature in solution (-120 degrees C), a reactive intermediate consistent with a bis-mu-oxodicopper(III)phenolate complex, with the O-O bond fully cleaved, is observed experimentally. The subsequent hydroxylation step has the hallmarks of an electrophilic aromatic substitution mechanism, similar to tyrosinase. Overall, the evidence for sequential O-O bond cleavage and C-O bond formation in this synthetic complex suggests an alternative intimate mechanism to the concerted or late stage O-O bond scission generally accepted for the phenol hydroxylation reaction performed by tyrosinase.