Deciphering the Thiolactonization Mechanism in Thiolactomycin Biosynthesis
Jiawei Guo, Qiaoyu Zhang, Yang Shen, Fangyuan Cheng, Moli Sang, Xuan Wang, Yunjun Pan, Mingyu Liu, Hao‐Bing Yu, Bo Hu, Sheng Wang, Liangzhen Zheng, Ce Geng, Chaofan Yang, Lianzhong Luo, Gang Zhang, Lei Du, Yuanning Li, Wei Zhang, Yandong Zhang, Binju Wang, Shengying Li, Xingwang Zhang
Abstract
Thiolactomycin ( 1 ), which features a unique γ-thiolactone ring, is a promising antibiotic candidate that specifically targets bacterial type II fatty acid synthase. Despite extensive studies on its pharmacological activities, modes of action, and chemical synthesis, the enzymatic processes responsible for forming the activity-determining γ-thiolactone ring have remained largely unknown. Here, we resolve this problem by revealing that the condensation and heterocyclization (Cy) domain of the nonribosomal peptide synthetase (NRPS) TlnC (TlnC Cy ), along with the cytochrome P450 enzyme TlnA, cooperatively enable the γ-thiolactone assembly. TlnC Cy mediates an unusual sulfurtransfer reaction to sulfurate the polyketide intermediate, generating a thiocarboxylate intermediate. Subsequently, TlnA acts as a γ-thiolactone synthase, converting the linear thiocarboxylate intermediate into 1 via a distal radical-based cyclization mechanism. These findings not only expand the functional and catalytic repertoires of NRPS Cy domains and P450 enzymes but also highlight a special enzymatic strategy for γ-thiolactone biosynthesis in nature.