Nature forms S-S bonds by oxidizing two sulfhydryl groups, and no enzyme installing an intact hydropersulfide (-SSH) group into a natural product has been identified to date. The leinamycin (LNM) family of natural products features intact S-S bonds, and previously we reported an SH domain (LnmJ-SH) within the LNM hybrid nonribosomal peptide synthetase (NRPS)-polyketide synthase (PKS) assembly line as a cysteine lyase that plays a role in sulfur incorporation. Here we report the characterization of an S-adenosyl methionine (SAM)-dependent hydropersulfide methyltransferase (GnmP) for guangnanmycin (GNM) biosynthesis, discovery of hydropersulfides as the nascent products of the GNM and LNM hybrid NRPS-PKS assembly lines, and revelation of three SH domains (GnmT-SH, LnmJ-SH, and WsmR-SH) within the GNM, LNM, and weishanmycin (WSM) hybrid NRPS-PKS assembly lines as thiocysteine lyases. Based on these findings, we propose a biosynthetic model for the LNM family of natural products, featuring thiocysteine lyases as PKS domains that directly install a -SSH group into the GNM, LNM, or WSM polyketide scaffold. Genome mining reveals that SH domains are widespread in Nature, extending beyond the LNM family of natural products. The SH domains could also be leveraged as biocatalysts to install an -SSH group into other biologically relevant scaffolds.

自然界通过氧化两个巯基形成 S-S 键，迄今为止尚未发现将完整的氢过硫醚 （-SSH） 基团安装到天然产物中的酶。天然产物的 leinamycin （LNM） 家族具有完整的 SS 键，之前我们报道了 LNM 杂交非核糖体肽合成酶 （NRPS）-聚酮合酶 （PKS） 装配线中的 SH 结构域 （LnmJ-SH） 作为半胱氨酸裂解酶，在硫掺入中发挥作用。在这里，我们报告了用于广南霉素 （GNM） 生物合成的 S-腺苷甲硫氨酸 （SAM） 依赖性氢过硫醚甲基转移酶 （GnmP） 的表征，发现氢过硫化物作为 GNM 和 LNM 杂交 NRPS-PKS 装配线的新兴产物，以及揭示 GNM、LNM 和微山霉素 （WSM） 杂交 NRPS-PKS 装配线中的三个 SH 结构域（GnmT-SH、LnmJ-SH 和 WsmR-SH）作为硫代半胱氨酸裂解酶。基于这些发现，我们为天然产物 LNM 家族提出了一种生物合成模型，以硫代半胱氨酸裂解酶作为 PKS 结构域，将 -SSH 基团直接安装到 GNM、LNM 或 WSM 聚酮支架中。基因组挖掘表明，SH 结构域在自然界中广泛存在，超出了天然产物的 LNM 家族。SH 结构域也可以用作生物催化剂，将 -SSH 基团安装到其他生物学相关的支架中。