Dimethylsulfoniopropionate (DMSP) is an abundant marine organosulfur compound with roles in stress protection, chemotaxis, nutrient and sulfur cycling and climate regulation. Here we report the discovery of a bifunctional DMSP biosynthesis enzyme, DsyGD, in the transamination pathway of the rhizobacterium Gynuella sunshinyii and some filamentous cyanobacteria not previously known to produce DMSP. DsyGD produces DMSP through its N-terminal DsyG methylthiohydroxybutyrate S-methyltransferase and C-terminal DsyD dimethylsulfoniohydroxybutyrate decarboxylase domains. Phylogenetically distinct DsyG-like proteins, termed DSYE, with methylthiohydroxybutyrate S-methyltransferase activity were found in diverse and environmentally abundant algae, comprising a mix of low, high and previously unknown DMSP producers. Algae containing DSYE, particularly bloom-forming Pelagophyceae species, were globally more abundant DMSP producers than those with previously described DMSP synthesis genes. This work greatly increases the number and diversity of predicted DMSP-producing organisms and highlights the importance of Pelagophyceae and other DSYE-containing algae in global DMSP production and sulfur cycling.

二甲基磺基丙酸酯 (DMSP) 是一种丰富的海洋有机硫化合物，在应激保护、趋化性、养分和硫循环以及气候调节方面发挥作用。在这里，我们报告了在根际 Gynuella sunshinyii 根际细菌和一些以前不知道产生 DMSP 的丝状蓝细菌的转氨途径中发现了双功能 DMSP 生物合成酶 DsyGD。 DsyGD 通过其 N 端 DsyG 甲硫基羟基丁酸 S-甲基转移酶和 C 端 DsyD 二甲基磺酰羟基丁酸脱羧酶结构域产生 DMSP。在多种且环境丰富的藻类中发现了系统发育上独特的 DsyG 样蛋白（称为 DSYE），具有甲硫基羟基丁酸 S-甲基转移酶活性，这些藻类包括低、高和以前未知的 DMSP 生产者的混合物。含有 DSYE 的藻类，特别是形成水花的海洋藻类物种，在全球范围内是比具有先前描述的 DMSP 合成基因的藻类更丰富的 DMSP 生产者。这项工作极大地增加了预测的 DMSP 生产生物体的数量和多样性，并强调了 Pelagophyceae 和其他含 DSYE 的藻类在全球 DMSP 生产和硫循环中的重要性。