论文总字数：29448字

摘 要

真菌毒素是威胁全球粮食安全一个重要因素，但发掘降解此类毒素的酶却困难重重。玉米赤霉烯酮（ZEN）是一种常见的真菌毒素，它的降解有赖于发现高效的降解菌株，后者产生解毒酶将毒素降解成为毒性小或者无毒的代谢产物。但是微生物种类繁多，起到降解玉米赤霉烯酮作用的是哪些酶、有哪些降解产物、降解途径是什么等问题，还有待我们进一步研究。

本研究针对玉米赤霉烯酮这一常见真菌毒素，通过检索文献报道的降解ZEN的水解酶ZHD101确定了解毒菌株Clonostachys rosea，并获得了它的基因组信息；通过细致地注释基因功能、分析有关代谢通路，我们筛选出若干相关的解毒酶，并构建了解毒酶的FASTA格式数据库。作为一个例子，本文还通过玉米赤霉烯酮降解途径中可能的中间产物—间苯二酚—为切入点，共筛选出了14个解毒酶蛋白质序列。本文的工作为进一步的解毒实验的验证研究提供了参考。

关键词：玉米赤霉烯酮；解毒酶；全基因组预测

Building the detoxification enzyme database from the genome data: a case study of zearalenone degradation

Abstract

Mycotoxins are the most widely spread toxins that threaten global food security. However, it is usually difficult to discover enzymes that can effectively degrade such toxins. For example, zearalenone (ZEN), as a typical mycotoxin, its degradation heavily depends on the discovery of efficient detoxification strains, which produces detoxification enzymes that bring down the toxins into small weak toxic or non-toxic metabolites. However, searching detoxification microorganisms, determining candidate enzymes, the fragmentized products and the relevant degradation pathway, may consume a large amount of time and efforts.

In this study, a genome-data based computational method was developed to screen candidate detoxification enzymes, taking ZEN degradation as an example. Specifically, we identified the detoxification strain , Clonostachys rosea, by retrieving the published enzyme ZHD101 -- the hydrolytic enzyme that breaks ZEN down from close form into a linear form, and obtained its genome information. By carefully annotating the function of genes encoded in the genome and analyzing the corresponding metabolic pathways, we successfully found a bunch of highly relevant detoxification enzymes. The FASTA format database of the identified detoxification enzymes was built. As a result, 14 protein sequences of candidate detoxification enzymes were discovered involving the intermediate product of zearalenone—the resorcinol. Our calculations provides a new data which makes further straightforward verification experiments possible to attack the ZEN-biodegradation problem.

Keywords: zearalenone; detoxification enzymes; genome annotation; enzyme database; resorcinol

目 录

摘 要 2

Abstract 3

第一章 绪论 4

1.1真菌毒素 4

1.2玉米赤霉烯酮 4

1.3玉米赤霉烯酮的脱毒 6

1.4 玉米赤霉烯酮中的间苯二酚的结构 9

1.5 全基因组预测 10

1.6本课题研究意义 12

第二章 思路与方法 13

2.1获取基因组 13

2.2基因组结构与功能注释 13

2.3代谢通路分析 14

2.4筛选解毒相关酶 16

2.5、构建fasta数据库 17

第三章 实验结果 19

3.1 注释可降解ZEN的菌株基因组 19

3.2 解毒相关酶的蛋白质序列 19

第四章 结论与展望 30

4.1 结论 30

4.2 存在的问题及优化手段 30

参考文献 32

致谢 36

绪论

1.1真菌毒素

真菌毒素是由真菌产生的一系列有害代谢产物，广泛存在于植物性产品中，是由曲霉属、青霉属、镰刀菌属等真菌产生的一类次级代谢产物^[1-2]。目前，自然界中己经发现的真菌毒素有300多种，其中有些真菌毒素对动物和人都有很强的致崎作用、致癌作用、遗传毒性、肝毒性、肾毒性、生殖素乱和免疫抑制等毒性作用，甚至引起人和动物的死亡^[3]。据美国食品和药物管理局估计，每年由于真菌毒素污染的带来的作物减产造成的经济损失平均高达9.32亿美元^[4]。最具代表性的真菌毒素有黄曲霉毒素、玉米赤霉烯酮、伏马毒素、赭曲霉毒素、单端孢酶烯族毒素等^[5]。

1.2玉米赤霉烯酮

请支付后下载全文，论文总字数：29448字