Characterization of pisatin-inducible cytochrome P450s in fungal pathogens of pea that detoxify the pea phytoalexin pisatin
Characterization of pisatin-inducible cytochrome P450s in fungal pathogens of pea that detoxify the pea phytoalexin pisatin
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DOI：
10.1006/fgbi.2001.1270
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发表时间：
2001-06-01
影响因子：
3
通讯作者：
VanEtten, HD
中科院分区：
文献类型：
--
作者：
George, HL;VanEtten, HD
许多对豌豆有致病作用的真菌都有能力去甲基化，从而使豌豆植物抗毒素pisatin解毒。这种解毒反应在红球线虫MP VI中被研究得最彻底，在那里它作为一种毒力特征发挥作用。催化这一反应的酶[pisatin脱甲基酶(PDA)]是细胞色素P450。在本研究中，比较了豌豆病原菌Ascochyta Pisi、Mycosphaerella Pinodes和Phoma Pinodella的微体制剂中对全细胞PDA活性的诱导和PDA的生化性质，并与红球菌产生的PDA进行了比较。根据辅因子的需求以及一氧化碳、细胞色素P450抑制剂和NAD-PH：细胞色素P450还原酶抗体的抑制作用，我们得出结论，来自其他豌豆病原菌的PDA也是细胞色素P450。所有这些酶都表现出对pisatin的选择性诱导，对pisatin具有较低的K-m，并且对pisatin作为底物具有相当高的专一性，这表明每个病原菌可能都有一个特异的细胞色素P450来解毒这种植物抗生素。由于这些真菌中的PDA对P450抑制剂的敏感性模式不同，并表现出其他微小的生化差异，我们认为这些真菌可能独立地进化出一种特殊的细胞色素P450作为共同宿主的毒力特征。(C)2001年学术出版社。
Many fungi that are pathogenic on pea have the ability to demethylate and thus detoxify the pea phytoalexin pisatin. This detoxification reaction has been studied most thoroughly in Nectria haematococca MP VI where it functions as a virulence trait. The enzyme catalyzing this reaction [pisatin demethylase (pda)] is a cytochrome P450. In the current study, the induction of whole-cell pda activity and the biochemical properties of pda in microsomal preparations from the pea pathogens Ascochyta pisi, Mycosphaerella pinodes, and Phoma pinodella are compared to the pda produced by N. haematococca. Based on cofactor requirements and their inhibition by carbon monoxide, cytochrome P450 inhibitors, and antibodies to NAD-PH:cytochrome P450 reductase, we conclude that the pdas from the other pea pathogens also are cytochrome P450s. All of the enzymes show a rather selective induction by pisatin, have a low K-m toward pisatin, and have a fairly high degree of specificity toward pisatin as a substrate, suggesting that each pathogen may have a specific cytochrome P450 for detoxifying this plant antibiotic. Since the pdas in these fungi differ in their pattern of sensitivity to P450 inhibitors and display other minor biochemical differences, we suggest that these fungi may have independently evolved a specialized cytochrome P450 as a virulence trait for a common host. (C) 2001 Academic Press.