Notomastus lobatus chloroperoxidase and Amphitrite ornata dehaloperoxidase both contain histidine as their proximal heme iron ligand.
Notomastus lobatus chloroperoxidase and Amphitrite ornata dehaloperoxidase both contain histidine as their proximal heme iron ligand.
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Notomastus lobatus 氯过氧化物酶和 Amphitrite ornata 脱卤过氧化物酶均含有组氨酸作为其近端血红素铁配体。
DOI：
10.1021/bi9621371
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发表时间：
1997
期刊：
影响因子：
--
通讯作者：
Dawson,JH
中科院分区：
文献类型：
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作者：
Roach,MP;Chen,YP;Woodin,SA;Lincoln,DE;Lovell,CR;Dawson,JH
最近从海洋来源中分离出了两种新的含血红素的过氧化物酶，一种能够将卤素结合到芳香底物中，另一种能够去除卤素，并由Chen等人初步表征。[(1991)J.Biol.化学。23909−23915；(1996年)J.Biol.化学。271,4609−4612]。卤代过氧化物酶(NCPO)在过氧化物酶活性中需要黄素蛋白成分是不寻常的。脱卤素过氧化物酶(DHP)是目前已知的唯一一种能够去除包括氟在内的卤素的含血红素的过氧化氢脱卤酶。这两种酶也非常不典型，因为它们含有血红素的亚基的相对分子质量小于16 000，大约是典型的含有血红素的过氧化物酶大小的一半到五分之一。有趣的是，我们还发现，尽管所有的蛋白质纯化都是在没有任何还原剂的情况下进行的，但这两种酶都是以含氧状态分离出来的。在本研究中，我们用磁性圆二色谱和UV−可见光吸收光谱研究了这两种酶，以确定它们近端的血红素铁配体的同一性。每种酶的四种衍生物，氰基铁、脱氧亚铁、含氧亚铁和(一氧化碳)亚铁，都被检测出来，并与肌红蛋白的平行衍生物进行了光谱比较，肌红蛋白是一种研究得很好的组氨酸连接的血红素蛋白。观察到的这两种新酶的每一种衍生物的光谱都非常相似，反过来，也与肌红蛋白的相同衍生物的光谱非常相似。我们得出的结论是，这两种新的血红素酶都含有组氨酸作为其近端的血红素铁配体。这使得NCPO成为第一个组氨酸连接的含血红素的过氧化物酶，能够使用氯作为卤素供体氯化卤素受体底物。此外，DHP的新反应活性并不是不寻常的近端配体的结果。目前对NCPO和DHP的结果挑战了目前关于含血红素的过氧化物酶如何发挥作用的教条： 一种是氯化底物，没有硫酸盐近端配体，另一种是含氧物和脱卤代卤代芳香族化合物，但像许多其他过氧化物酶一样，具有组氨酸近端配体，不能进行这样的组合反应。
Two novel heme-containing peroxidases, one able to incorporate halogens into aromatic substrates and the other able to remove them, have recently been isolated from marine sources and initially characterized by Chen et al. [(1991)J. Biol. Chem. 266, 23909−23915; (1996)J.Biol. Chem. 271, 4609−4612]. The haloperoxidaseNotomastus lobatuschloroperoxidase (NCPO) is unusual in requiring a flavoprotein component for peroxidase activity. The dehaloperoxidase (DHP), isolated fromAmphitrite ornata, is the only heme-containing peroxide-dependent dehalogenase known to be capable of removing halogens including fluorine. Both enzymes are also quite atypical in that the molecular weights of their heme-containing subunits are less than 16 000, approximately one-half to one-fifth the size of typical heme-containing peroxidases. Interestingly, we have also found that both enzymes are isolated in their oxyferrous states even though all protein purification was done in the absence of any reductant. In the present study, we have examined these two enzymes with magnetic circular dichroism and UV−visible absorption spectroscopy in order to determine the identity of their proximal heme iron ligand. Four derivatives of each enzyme, cyanoferric, deoxyferrous, oxyferrous, and (carbonmonoxy)ferrous, have been examined and spectroscopically compared to parallel derivatives of myoglobin, a well-studied histidine-ligated heme protein. The spectra observed for each derivative of the two new enzymes are very similar to each other and, in turn, to the spectra of the same derivatives of myoglobin. We conclude that both new heme enzymes contain histidine as their proximal heme iron ligand. This makes NCPO the first histidine-ligated heme-containing peroxidase capable of chlorinating halogen acceptor substrates using chloride as the halogen donor. Further, the novel reactivity of DHP is not the result of an unusual proximal ligand. The present results with NCPO and DHP challenge the current dogma of how heme-containing peroxidases function: one chlorinates substrates without having a thiolate proximal ligand, and the other both oxygenates and dehalogenates haloaromatics and yet has a histidine proximal ligand like numerous other peroxidases that are not capable of such a combined reactivity.