Discovery and characterization of a marine bacterial SAM-dependent chlorinase
Discovery and characterization of a marine bacterial SAM-dependent chlorinase
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DOI：
10.1038/nchembio.2007.56
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发表时间：
2008-01-01
影响因子：
14.8
通讯作者：
Moore, Bradley S.
中科院分区：
文献类型：
--
作者：
Eustaquio, Alessandra S.;Pojer, Florence;Moore, Bradley S.
将卤素原子掺入生物活性化合物的支架中通常会增强生物活性，例如抗癌剂salinosporamide A（1），一种来自海洋细菌Salinispora tropica的氯化天然产物。在理解酶氯化方面的重大努力表明，氧化途径占主导地位，形成反应性亲电或自由基氯物种。在这里，我们报告了氯化酶SaIL的遗传、生化和结构特征，该酶以类似于链霉菌氟化酶的罕见亲核取代策略用氯化物卤化S-腺苷-L-甲硫氨酸（2）以产生5 '-氯-5'-脱氧腺苷（3）和L-甲硫氨酸（4）。进一步的代谢剪裁产生对盐孢菌酰胺A生物合成特异的卤化聚酮合酶底物。SaIL也接受溴化物和碘化物作为底物，但不接受氟化物。SAL和活性位点突变体与底物和产物复合的高分辨率晶体结构支持S（N）2亲核取代机制，并进一步阐明了这个新发现的卤化酶家族中的卤化物特异性。
Halogen atom incorporation into a scaffold of bioactive compounds often amplifies biological activity, as is the case for the anticancer agent salinosporamide A (1), a chlorinated natural product from the marine bacterium Salinispora tropica. Significant effort in understanding enzymatic chlorination shows that oxidative routes predominate to form reactive electrophilic or radical chlorine species. Here we report the genetic, biochemical and structural characterization of the chlorinase SaIL, which halogenates S-adenosyl-L-methionine (2) with chloride to generate 5'-chloro-5'-deoxyadenosine (3) and L-methionine (4) in a rarely observed nucleophilic substitution strategy analogous to that of Streptomyces cattleya fluorinase. Further metabolic tailoring produces a halogenated polyketide synthase substrate specific for salinosporamide A biosynthesis. SaIL also accepts bromide and iodide as substrates, but not fluoride. High-resolution crystal structures of SAL and active site mutants complexed with substrates and products support the S(N)2 nucleophilic substitution mechanism and further illuminate halide specificity in this newly discovered halogenase family.