REDUCTIVE DETOXIFICATION AS A MECHANISM OF FUNGAL RESISTANCE TO SINGLET OXYGEN-GENERATING PHOTOSENSITIZERS
REDUCTIVE DETOXIFICATION AS A MECHANISM OF FUNGAL RESISTANCE TO SINGLET OXYGEN-GENERATING PHOTOSENSITIZERS
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DOI：
10.1073/pnas.89.20.9588
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发表时间：
1992-10-15
影响因子：
11.1
通讯作者：
BOWDEN, EF
中科院分区：
文献类型：
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作者：
DAUB, ME;LEISMAN, GB;BOWDEN, EF
对产生单线态氧的毒素尾孢菌素具有抗性或敏感性的真菌被测定其通过还原来解毒的能力。通过使用带通滤光片在显微镜下测定尾孢菌素还原，以区分尾孢菌素和还原尾孢菌素的荧光发射。抗性尾孢菌属和链格孢属物种的菌丝发出绿色荧光，指示减少的尾孢菌素。不能存活的培养物和尾孢菌素敏感的真菌的菌丝不能减少尾孢菌素。敏感真菌偶尔减少尾孢菌素时，温育的还原剂，保护对尾孢菌素毒性。在没有真菌的情况下，尾孢菌素不能被有效地光还原。尾孢菌属对曙红Y也有抗性，但对玫瑰红敏感。显微镜观察表明尾孢菌属不能还原虎红，但能还原曙红Y。这些观察结果得到了体外电化学测量的支持，该测量揭示了以下顺序：尾孢菌素>>曙红Y >虎红。尾孢菌素在pH7.5时的表观氧化还原电位（E-度）为-0.14V。我们的结论是尾孢菌物种保护自己免受尾孢毒素分子的还原和解毒。
Fungi that are resistant or sensitive to the singlet oxygen-generating toxin cercosporin were assayed for their ability to detoxify it by reduction. Cercosporin reduction was assayed microscopically by using bandpass filters to differentiate between fluorescence emission from cercosporin and reduced cercosporin. Hyphae of the resistant Cercospora and Alternaria species emitted a green fluorescence, indicative of reduced cercosporin. Hyphae of nonviable cultures and of cercosporin-sensitive fungi did not reduce cercosporin. Sensitive fungi occasionally reduced cercosporin when incubated with reducing agents that protect against cercosporin toxicity. Cercosporin could not be efficiently photoreduced in the absence of the fungus. Cercospora species were also resistant to eosin Y but were sensitive to rose bengal. Microscopic observation demonstrated that Cercospora species were not capable of reducing rose bengal but were capable of reducing eosin Y. These observations were supported by in vitro electrochemical measurements that revealed the following order with respect to ease of reduction: cercosporin >> eosin Y > rose bengal. The formal redox potential (E-degrees') of cercosporin at pH 7.5 was found to be -0.14 V vs. the normal hydrogen electrode. We conclude that Cercospora species protect themselves against cercosporin by the reduction and detoxification of the toxin molecule.