Chirality, a fundamental property of matter, is often overlooked in the studies of marine organic matter cycles. Dihydroxypropanesulfonate (DHPS), a globally abundant organosulfur compound, serves as an ecologically important currency for nutrient and energy transfer from phytoplankton to bacteria in the ocean. However, the chirality of DHPS in nature and its transformation remain unclear. Here, we developed a novel approach using chiral phosphorus-reagent labeling to separate DHPS enantiomers. Our findings demonstrated that at least one enantiomer of DHPS is present in marine diatoms and coccolithophores, and that both enantiomers are widespread in marine environments. A novel chiral-selective DHPS catabolic pathway was identified in marine Roseobacteraceae strains, where HpsO and HpsP dehydrogenases at the gateway to DHPS catabolism act specifically on R-DHPS and S-DHPS, respectively. R-DHPS is also a substrate for the dehydrogenase HpsN. All three dehydrogenases generate stable hydrogen bonds between the chirality-center hydroxyls of DHPS and highly conserved residues, and HpsP also form coordinate-covalent bonds between the chirality-center hydroxyls and Zn2+, which determines the mechanistic basis of strict stereoselectivity. We further illustrated the role of enzymatic promiscuity in the evolution of DHPS metabolism in Roseobacteraceae and SAR11. This study provides the first evidence of chirality's involvement in phytoplankton-bacteria metabolic currencies, opening a new avenue for understanding the ocean organosulfur cycle.

中文翻译：

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海洋细菌对浮游植物来源的二羟基丙磺酸盐的对映选择性转化

手性是物质的基本属性，在海洋有机物循环的研究中经常被忽视。二羟基丙烷磺酸盐 (DHPS) 是一种全球丰富的有机硫化合物，是海洋中从浮游植物到细菌的营养和能量转移的重要生态货币。然而，DHPS在自然界中的手性及其转化仍不清楚。在这里，我们开发了一种使用手性磷试剂标记来分离 DHPS 对映体的新方法。我们的研究结果表明，海洋硅藻和颗石藻中至少存在 DHPS 的一种对映体，并且这两种对映体在海洋环境中广泛存在。在海洋玫瑰杆菌科菌株中发现了一种新型手性选择性 DHPS 分解代谢途径，其中 DHPS 分解代谢门户的 HpsO 和 HpsP 脱氢酶分别专门作用于 R-DHPS 和 S-DHPS。 R-DHPS 也是脱氢酶 HpsN 的底物。三种脱氢酶均在DHPS的手性中心羟基与高度保守的残基之间产生稳定的氢键，并且HpsP也在手性中心羟基与Zn2+之间形成配位共价键，这决定了严格立体选择性的机制基础。我们进一步阐明了酶混杂在玫瑰杆菌科和 SAR11 DHPS 代谢进化中的作用。这项研究提供了手性参与浮游植物-细菌代谢货币的第一个证据，为理解海洋有机硫循环开辟了新途径。