Department of Chemistry, Texas A&M University , College Station, Texas 77843, United States.
Department of Microbial Natural Products, Helmholtz Institute for Pharmaceutical Research Saarland, Helmholtz Center for Infection Research, Saarland University , Universitätscampus E8.1, D-66123 Saarbrücken, Germany.
J Am Chem Soc. 2017 Feb 8;139(5):1742-1745. doi: 10.1021/jacs.6b10901. Epub 2017 Jan 25.
The biosynthesis of branched alkoxy groups, such as the unique t-butyl group found in a variety of natural products, is still poorly understood. Recently, cystobactamids were isolated and identified from Cystobacter sp as novel antibacterials. These metabolites contain an isopropyl group proposed to be formed using CysS, a cobalamin-dependent radical S-adenosylmethionine (SAM) methyltransferase. Here, we reconstitute the CysS-catalyzed reaction, on p-aminobenzoate thioester substrates, and demonstrate that it not only catalyzes sequential methylations of a methyl group to form ethyl and isopropyl groups but remarkably also sec-butyl and t-butyl groups. To our knowledge, this is the first in vitro reconstitution of a cobalamin-dependent radical SAM enzyme catalyzing the conversion of a methyl group to a t-butyl group.
支链烷氧基的生物合成，如各种天然产物中独特的叔丁基，仍然知之甚少。最近，从粘质沙雷氏菌中分离并鉴定出胱硫醚作为新型抗菌药物。这些代谢物含有异丙基，据推测是使用 CysS，一种钴胺素依赖的自由基 S-腺苷甲硫氨酸（SAM）甲基转移酶形成的。在这里，我们在对氨基苯甲酸硫酯底物上重新构建了 CysS 催化的反应，并证明它不仅催化一个甲基的顺序甲基化形成乙基和异丙基，而且还显著地形成仲丁基和叔丁基。据我们所知，这是首例体外重建催化甲基转化为叔丁基的钴胺素依赖的自由基 SAM 酶。
