Baudouin E, Charpenteau M, Roby D, Marco Y, Ranjeva R, Ranty B
Laboratoire Signaux et Messages Cellulaires chez les Végétaux, UMR 5546 CNRS, Université Paul Sabatier, Toulouse, France.
Eur J Biochem. 1997 Sep 15;248(3):700-6. doi: 10.1111/j.1432-1033.1997.t01-1-00700.x.
We have recently reported the isolation of a tobacco gene, hsr 203J, whose transcripts accumulate during the hypersensitive reaction, a plant response associated with resistance to pathogens. We present and discuss here some structural and biochemical properties of the gene product. Nucleotide sequence analysis has shown that the hsr 203J gene contains an open reading frame coding for a polypeptide of 335 amino acids. The predicted amino acid sequence contains the GXSXG motif characteristic of serine hydrolases, and displays limited but significant similarity to lipases and esterases of prokaryotic origin. The hsr 203J gene was expressed in Escherichia coli, and the recombinant protein, purified to near homogeneity, was able to degrade p-nitrophenylbutyrate, a general substrate for carboxylesterases. The enzyme was unable to hydrolyze lipids, and was active on short-chain acyl esters only. The hydrolytic activity was abolished by diisopropyl fluorophosphate and a derivative of isocoumarin, as expected for a member of the serine hydrolase family. Sequence similarities between the tobacco esterase and expressed sequence tags in databases suggest the existence of members of this enzyme family in various plant species.
我们最近报道了一个烟草基因hsr 203J的分离，其转录本在过敏反应期间积累，过敏反应是一种与植物对病原体抗性相关的反应。我们在此展示并讨论该基因产物的一些结构和生化特性。核苷酸序列分析表明，hsr 203J基因包含一个编码335个氨基酸多肽的开放阅读框。预测的氨基酸序列包含丝氨酸水解酶特有的GXSXG基序，并且与原核生物来源的脂肪酶和酯酶有有限但显著的相似性。hsr 203J基因在大肠杆菌中表达，纯化至接近均一的重组蛋白能够降解对硝基苯丁酸，这是羧酸酯酶的一种通用底物。该酶不能水解脂质，并且仅对短链酰基酯有活性。正如丝氨酸水解酶家族成员所预期的那样，二异丙基氟磷酸酯和异香豆素衍生物消除了其水解活性。烟草酯酶与数据库中表达序列标签之间的序列相似性表明，该酶家族的成员存在于各种植物物种中。
