Mechanistic Insights into the Radical S-adenosyl-l-methionine Enzyme NosL From a Substrate Analogue and the Shunt Products
Mechanistic Insights into the Radical S-adenosyl-l-methionine Enzyme NosL From a Substrate Analogue and the Shunt Products
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从底物类似物和分流产品中深入了解自由基 S-腺苷-L-甲硫氨酸酶 NosL 的机理。
DOI：
10.1002/anie.201509900
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发表时间：
2016-03-01
影响因子：
16.6
通讯作者：
Zhang, Qi
中科院分区：
文献类型：
--
作者：
Ji, Xinjian;Li, Yongzhen;Zhang, Qi
自由基S-腺苷-L-甲硫氨酸（SAM）酶NosL催化L-色氨酸转化为3-甲基-2-吲哚酸（MIA），MIA是临床上感兴趣的抗生素那西肽生物合成的关键中间体。以NosL为催化剂，研究了底物类似物2-甲基-3-（吲哚-3-基）丙酸（MIPA）对NosL催化反应的影响。在D2 O和H2 O中用不同的MIPA同位素异构体进行的生化测定明确地表明，5 '-脱氧腺苷（dAdo）自由基介导的氢提取来自l-色氨酸的氨基，而不是蛋白质残基。令人惊讶的是，二氢自由基介导的夺氢发生在MIPA的两个不同位点，从而将底物划分为不同的反应途径。结合α，β-不饱和酮分流产物的鉴定，我们的研究为NosL催化提供了有价值的机理见解，并突出了自由基SAM酶显着的催化灵活性。
The radical S-adenosyl-l-methionine (SAM) enzyme NosL catalyzes the transformation of l-tryptophan into 3-methyl-2-indolic acid (MIA), which is a key intermediate in the biosynthesis of a clinically interesting antibiotic nosiheptide. NosL catalysis was investigated by using the substrate analogue 2-methyl-3-(indol-3-yl)propanoic acid (MIPA), which can be converted into MIA by NosL. Biochemical assays with different MIPA isotopomers in D2 O and H2 O unambiguously indicated that the 5'-deoxyadenosyl (dAdo)-radical-mediated hydrogen abstraction is from the amino group of l-tryptophan and not a protein residue. Surprisingly, the dAdo-radical-mediated hydrogen abstraction occurs at two different sites of MIPA, thereby partitioning the substrate into different reaction pathways. Together with identification of an α,β-unsaturated ketone shunt product, our study provides valuable mechanistic insight into NosL catalysis and highlights the remarkable catalytic flexibility of radical SAM enzymes.