State Key Laboratory of Protein and Plant Gene Research, Peking-Yale Joint Center for Plant Molecular Genetics and Agrobiotechnology, College of Life Sciences, Peking University, Beijing, People's Republic of China.
PLoS One. 2011 Mar 31;6(3):e18300. doi: 10.1371/journal.pone.0018300.
Cyanate is toxic to all organisms. Cyanase converts cyanate to CO₂ and NH₃ in a bicarbonate-dependent reaction. The biophysical functions and biochemical characteristics of plant cyanases are poorly studied, although it has been investigated in a variety of proteobacteria, cyanobacteria and fungi. In this study, we characterised plant cyanases from Arabidopsis thaliana and Oryza sativa (AtCYN and OsCYN). Prokaryotic-expressed AtCYN and OsCYN both showed cyanase activity in vitro. Temperature had a similar influence on the activity of both cyanases, but pH had a differential impact on AtCYN and OsCYN activity. Homology modelling provided models of monomers of AtCYN and OsCYN, and a coimmunoprecipitation assay and gel filtration indicated that AtCYN and OsCYN formed homodecamers. The analysis of single-residue mutants of AtCYN indicated that the conserved catalytic residues also contributed to the stability of the homodecamer. KCNO treatment inhibited Arabidopsis germination and early seedling growth. Plants containing AtCYN or OsCYN exhibited resistance to KCNO stress, which demonstrated that one role of cyanases in plants is detoxification. Transcription level of AtCYN was higher in the flower than in other organs of Arabidopsis. AtCYN transcription was not significantly affected by KCNO treatment in Arabidopsis, but was induced by salt stress. This research broadens our knowledge on plant detoxification of cyanate via cyanase.
氰酸盐对所有生物都有毒性。氰酸酶在碳酸氢盐依赖的反应中将氰酸盐转化为 CO₂和 NH₃。尽管在多种变形菌、蓝藻和真菌中都对植物氰酸酶的生物物理功能和生化特性进行了研究，但对其了解仍很有限。在本研究中，我们对拟南芥和水稻中的植物氰酸酶进行了表征（AtCYN 和 OsCYN）。原核表达的 AtCYN 和 OsCYN 在体外均表现出氰酸酶活性。温度对两种氰酸酶的活性有相似的影响，但 pH 对 AtCYN 和 OsCYN 的活性有不同的影响。同源建模提供了 AtCYN 和 OsCYN 单体的模型，共免疫沉淀和凝胶过滤分析表明 AtCYN 和 OsCYN 形成同源十聚体。AtCYN 单点突变分析表明，保守的催化残基也有助于同源十聚体的稳定性。KCN0 处理抑制了拟南芥的萌发和早期幼苗生长。含有 AtCYN 或 OsCYN 的植物对 KCN0 胁迫表现出抗性，这表明氰酸酶在植物中的作用之一是解毒。AtCYN 的转录水平在拟南芥的花中高于其他器官。在拟南芥中，KCN0 处理对 AtCYN 的转录没有显著影响，但盐胁迫诱导了 AtCYN 的转录。这项研究拓宽了我们对植物通过氰酸酶解毒氰酸盐的认识。
