Function of halogenating enzymes and a biogenic halogen cycle in nature

包括珊瑚在内的一些海洋藻类产生的溴仿是一种化感物质，可以消除附生生物，特别是藻类表面的硅藻。另一方面，一些海洋大型和微型藻类如Paviova sp.也观察到一卤代甲烷的释放。在这些藻类中形成一卤代甲烷的分子表征表明，SAM：卤离子甲基转移酶反应参与了该反应。然而，这些酶非常不稳定，因此，进一步的表征一直是困难的。最近，我们发现了一种具有相对稳定酶的海洋微藻，并建立了分离它的纯化程序。这是从海洋微藻中分离纯化SAM：卤离子甲基转移酶的首次工作。海洋环境，特别是海洋微藻释放的甲基溴可以解释大气中甲基溴的含量。在本研究项目中，我们从土壤微生物恶臭假单胞菌中克隆了一种新的编码钴激活溴过氧化物酶的基因。该重组酶催化了苯乙烯和吲哚的溴化反应，生成了相应的外消旋溴代醇化合物。该酶对D-乙酰硫代异丁酸甲酯具有酯酶活性，是一种独特的双功能酶。

Bromoform produced by some marine algae including Corallina was found to be a kind of allelochemical eliminating the epiphytic organisms, especially, diatoms on the algal surface.On the other hand, monohalomethanes have been observed to emit from some marine macro- and microalgae such as Paviova sp. Molecular characterization to form monohalomethanes in these algae have revealed that SAM : halide ion methyltransferase reaction participates in the reaction. However, these enzymes were very unstable, therefaore, further characterization had been difficult. Recently, we have found a marine microalga having the relatively stable enzyme and established the purification procedures to isolate it. This is the first work to purify the SAM : halide ion methyltransferase from marine microalga. The emission of methyl bromide from marine environment, especially from marine microalgae, could explain the amount of methyl bromide in the atmosphere.In this research project, we have cloned the gene encoding a novel Co^<2+>-activating bromoperoxidase from a soil microorganism, Pseudomonas putida. The recombinant enzyme catalyzed the brominating reactions of styrene and indene giving the corresponding racemic bromohydrin compounds. It was also found that the enzyme has a esterase activity toward methyl D-acethylthioisobutyrate, suggesting that the enzyme is an unique bifunctional enzyme.