University of Amsterdam, Van't Hoff Institute for Molecular Sciences, Science Park 904, 1098 XH Amsterdam, The Netherlands.
Dalton Trans. 2013 Sep 7;42(33):11778-86. doi: 10.1039/c3dt50525a.
Vanadium haloperoxidases differ strongly from heme peroxidases in substrate specificity and stability and in contrast to a heme group they contain the bare metal oxide vanadate as a prosthetic group. These enzymes specifically oxidize halides in the presence of hydrogen peroxide into hypohalous acids. These reactive halogen intermediates will react rapidly and aspecifically with many organic molecules. Marine algae and diatoms containing these iodo- and bromoperoxidases produce short-lived brominated methanes (bromoform, CHBr3 and dibromomethane CH2Br2) or iodinated compounds. Some seas and oceans are supersaturated with these compounds and they form an important source of bromine to the troposphere and lower stratosphere and contribute significantly to the global budget of halogenated hydrocarbons. This perspective focuses, in particular, on the biosynthesis of these volatile compounds and the direct or indirect involvement of vanadium haloperoxidases in the production of huge amounts of bromoform and dibromomethane. Some of the global sources are discussed and from the literature a picture emerges in which oxidized brominated species generated by phytoplankton, seaweeds and cyanobacteria react with dissolved organic matter in seawater, resulting in the formation of intermediate brominated compounds. These compounds are unstable and decay via a haloform reaction to form an array of volatile brominated compounds of which bromoform is the major component followed by dibromomethane.
钒卤过氧化物酶在底物特异性和稳定性方面与血红素过氧化物酶有很大的不同，与血红素基团相反，它们含有裸露的金属氧化物钒酸盐作为辅基。这些酶在过氧化氢存在的情况下特异性地将卤化物氧化成次卤酸。这些反应性卤代中间体将快速、非特异性地与许多有机分子反应。含有这些碘代和溴过氧化物酶的海洋藻类和硅藻产生短寿命的溴代甲烷（三溴甲烷，CHBr3 和二溴甲烷 CH2Br2）或碘代化合物。一些海洋和海洋中这些化合物的饱和度很高，它们是向对流层和低层平流层提供溴的重要来源，并对卤代碳氢化合物的全球预算有重大贡献。本观点特别关注这些挥发性化合物的生物合成，以及钒卤过氧化物酶在大量三溴甲烷和二溴甲烷生成中的直接或间接参与。讨论了一些全球来源，从文献中可以看出，浮游植物、海藻和蓝藻产生的氧化溴化物与海水中的溶解有机物反应，形成中间溴代化合物。这些化合物不稳定，通过卤仿反应降解，形成一系列挥发性溴代化合物，其中三溴甲烷是主要成分，其次是二溴甲烷。
