Degradation of a peptide in pitcher fluid of the carnivorous plant Nepenthes alata Blanco
Degradation of a peptide in pitcher fluid of the carnivorous plant Nepenthes alata Blanco
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DOI：
10.1007/s00425-002-0768-7
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发表时间：
2002-07-01
期刊：
影响因子：
4.3
通讯作者：
Kobayashi, A
中科院分区：
文献类型：
--
作者：
An, CI;Takekawa, S;Kobayashi, A
食肉植物从昆虫那里获取大量的氮。热带食肉植物猪笼草在从叶端伸长的卷须尖端产生称为捕虫笼的捕获器官。捕虫笼底部分泌酸性液体。捕虫笼液中含有多种水解酶，其中一些酶（例如天冬氨酸蛋白酶）被认为参与从昆虫蛋白质中获取氮，以了解氮获取过程。识别罐液中的蛋白质降解产物至关重要。为了深入了解猪笼草捕虫笼液中的蛋白质降解情况，我们使用牛胰岛素的氧化 B 链作为模型底物，并使用液相色谱-质谱法 (LC-MS) 研究了翼猪笼草捕虫笼液对蛋白质的降解情况。降解产物的 LC-MS 分析表明，牛胰岛素的氧化 B 链最初在芳香族氨基酸（如苯丙氨酸和酪氨酸）处裂解。这些切割位点与其他植物和动物的天冬氨酸蛋白酶的切割位点相似。一系列作为降解产物的肽片段的存在表明外肽酶也存在于捕虫笼液中。降解产物的氨基酸分析和肽片段分析表明，牛胰岛素氧化B链中释放出3个氨基酸和小肽，表明昆虫蛋白在翼猪笼草捕虫笼液中很容易降解为小肽和氨基酸。
Carnivorous plants acquire substantial amounts of nitrogen from insects. The tropical carnivorous plant Nepenthes produces trapping organs called pitchers at the tips of tendrils elongated from leaf ends. Acidic fluid is secreted at the bottoms of the pitchers. The pitcher fluid includes several hydrolytic enzymes, and some, such as aspartic proteinase, are thought to be involved in nitrogen acquisition from insect proteins, To understand the nitrogen-acquisition process. it is essential to identify the protein-degradation products in the pitcher fluid. To gain insight into protein degradation in pitcher fluid, we used the oxidized B-chain of bovine insulin as a model substrate, and its degradation by the pitcher fluid of N. alata was investigated using liquid chromatography-mass spectrometry (LC-MS). LC-MS analysis of the degradation products revealed that the oxidized B-chain of bovine insulin was initially cleaved at aromatic amino acids such as phenylalanine and tyrosine. These cleavage sites are similar to those of aspartic proteinases from other plants and animals. The presence of a series of peptide fragments as degradation products suggests that exopeptidase(s) is also present in the pitcher fluid. Amino acid analysis and peptide fragment analysis of the degradation products demonstrated that three amino acids plus small peptides were released from the oxidized B-chain of bovine insulin, suggesting that insect proteins are readily degraded to small peptides and amino acids in the pitcher fluid of N. alata.