Department of Chemistry, Texas A&M University , College Station, Texas 77843, United States.
J Am Chem Soc. 2016 Dec 21;138(50):16184-16187. doi: 10.1021/jacs.6b06139. Epub 2016 Dec 8.
Tryptophan lyase (NosL) is a radical S-adenosyl-l-methionine (SAM) enzyme that catalyzes the formation of 3-methyl-2-indolic acid from l-tryptophan. In this paper, we demonstrate that the 5'-deoxyadenosyl radical is considerably more versatile in its chemistry than previously anticipated: hydrogen atom abstraction from N-cyclopropyltryptophan occurs at Cα rather than the amino group with NosL Y90A and replacing the substrate amine with a ketone or an alkene changes the chemistry from hydrogen atom abstraction to double bond addition. In addition, the 5'-deoxyadenosyl radical can add to the [4Fe-4S] cluster and dithionite can be used to trap radicals at the active site.
色氨酸裂解酶（NosL）是一种自由基 S-腺苷甲硫氨酸（SAM）酶，可催化 l-色氨酸生成 3-甲基-2-吲哚酸。在本文中，我们证明 5'-脱氧腺苷自由基在化学性质上比以前预期的更为多样：NosL Y90A 从 N-环丙基色氨酸中发生氢原子的提取发生在 Cα 而不是氨基，而用酮或烯烃取代底物胺会使化学性质从氢原子提取变为双键加成。此外，5'-脱氧腺苷自由基可以添加到 [4Fe-4S] 簇中，并且可以使用连二亚硫酸盐在活性位点捕获自由基。
