Cyanate is utilized by many microbes as an organic nitrogen source. The key enzyme for cyanate metabolism is cyanase, converting cyanate to ammonium and carbon dioxide. Although the cyanase gene cynS has been identified in many species, the diversity, prevalence, and expression of cynS in marine microbial communities remains poorly understood. Here, based on the full-length cDNA sequence of a dinoflagellate cynS and 260 homologs across the tree of life, we extend the conserved nature of cyanases by the identification of additional ultra-conserved residues as part of the modeled holoenzyme structure. Our phylogenetic analysis showed that horizontal gene transfer of cynS appears to be more prominent than previously reported for bacteria, archaea, chlorophytes, and metazoans. Quantitative analyses of marine planktonic metagenomes revealed that cynS is as prevalent as ureC (urease subunit alpha), suggesting that cyanate plays an important role in nitrogen metabolism of marine microbes. Highly abundant cynS transcripts from phytoplankton and nitrite-oxidizing bacteria identified in global ocean metatranscriptomes indicate that cyanases potentially occupy a key position in the marine nitrogen cycle by facilitating photosynthetic assimilation of organic N and its remineralisation to NO₃ by the activity of nitrifying bacteria.

许多微生物利用氰酸盐作为有机氮源。氰酸盐代谢的关键酶是氰酶，将氰酸盐转化为铵和二氧化碳。尽管氰酶基因cynS已在许多物种中被发现，但cynS在海洋微生物群落中的多样性、流行性和表达仍然知之甚少。在这里，基于甲藻cynS的全长 cDNA 序列和生命树中的 260 个同源物，我们通过将额外的超保守残基鉴定为模型全酶结构的一部分来扩展氰酶的保守性质。我们的系统发育分析表明，cynS的水平基因转移似乎比以前报道的细菌、古细菌、叶绿素和后生动物更突出。海洋浮游宏基因组的定量分析表明，cynS与ureC （脲酶亚基α）一样普遍，表明氰酸盐在海洋微生物的氮代谢中起重要作用。在全球海洋宏转录组中发现的来自浮游植物和亚硝酸盐氧化细菌的高度丰富的 cynS转录物表明，氰酶通过促进有机氮的光合作用同化并通过硝化细菌的活性再矿化为 NO _{3 ，从而可能在海洋氮循环中占据关键位置。}