Cobalamin, vitamin B₁₂, is an important micronutrient that has been investigated for decades in the marine context because it is required for phytoplankton growth. The biologically active forms (Me-B₁₂, Ado-B₁₂) and the synthetic form (CN-B₁₂) quickly convert to OH-B₁₂ after light exposure in various aqueous solutions, but puzzlingly have been frequently reported to dominate dissolved cobalamin pools in the sunlit ocean. Here, we document photodegradation timescales for these cobalamin forms in natural seawater using targeted mass spectrometry, providing quantitative evidence that OH-B₁₂ is expected to be the dominant dissolved form in irradiated seawater. Then, through high-resolution mass spectrometry, we identify four photodegradation products of OH-B₁₂ which represent potential building blocks microbes could salvage and remodel to satisfy cellular cobalamin requirements. Taken together, these results clarify the impact of light on marine cobalamin dynamics, laying a foundation for a more quantitative understanding of the role of cobalamin in microbial communities and biogeochemical cycles.

中文翻译：

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揭示海洋中钴胺素的光降解作用

钴胺素（维生素 B ₁₂）是一种重要的微量营养素，数十年来一直在海洋环境中进行研究，因为它是浮游植物生长所必需的。生物活性形式（Me-B ₁₂、Ado-B ₁₂）和合成形式（CN-B ₁₂）在各种水溶液中暴露于光后迅速转化为 OH-B ₁₂，但令人费解的是，经常有报道称其在溶解的钴胺素中占主导地位阳光照射下的海洋中的泳池。在这里，我们使用靶向质谱法记录了天然海水中这些钴胺素形式的光降解时间尺度，提供了 OH-B ₁₂预计将成为辐照海水中主要溶解形式的定量证据。然后，通过高分辨率质谱分析，我们确定了 OH-B ₁₂的四种光降解产物，它们代表微生物可以挽救和重塑以满足细胞钴胺素需求的潜在构建块。总而言之，这些结果阐明了光对海洋钴胺素动力学的影响，为更定量地了解钴胺素在微生物群落和生物地球化学循环中的作用奠定了基础。