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Ferric iron reduction by Cryptococcus neoformans.

机译：新型隐球菌还原铁。

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The pathogenic yeast Cryptococcus neoformans must reduce Fe(III) to Fe(II) prior to uptake. We investigated mechanisms of reduction using the chromogenic ferrous chelator bathophenanthroline disulfonate. Iron-depleted cells reduced 57 nmol of Fe(III) per 10(6) cells per h, while iron-replete cells reduced only 8 nmol of Fe(III). Exponential-phase cells reduced the most and stationary-phase cells reduced the least Fe(III), independent of iron status. Supernatants from iron-depleted cells reduced up to 2 nmol of Fe(III) per 10(6) cells per h, while supernatants from iron-replete cells reduced 0.5 nmol of Fe(III), implying regulation of the secreted reductant(s). One such reductant is 3-hydroxyanthranilic acid (3HAA), which was found at concentrations up to 29 microM in iron-depleted cultures but <2 microM in cultures supplemented with iron. Moreover, when washed and resuspended in low iron medium, iron-depleted cells secreted 20.4 microM 3HAA, while iron-replete cells secreted only 4.5 microM 3HAA. Each mole of 3HAA reduced 3 mol of Fe(III), and increasing 3HAA concentrations correlated with increasing reducing activity of supernatants; however, 3HAA accounted for only half of the supernatant's reducing activity, indicating the presence of additional reductants. Finally, we found that melanized stationary-phase cells reduced 2 nmol of Fe(III) per 10(6) cells per h--16 times the rate of nonmelanized cells--suggesting that this redox polymer participates in reduction of Fe(III).
机译：致病性酵母隐球菌必须在摄取前将Fe（III）还原为Fe（II）。我们研究了使用发色亚铁螯合剂双菲咯啉二磺酸盐的还原机理。贫铁细胞每h（10（6）个细胞）每小时可减少57 nmol的Fe（III），而贫铁细胞仅可减少8 nmol的Fe（III）。指数相电池还原的铁最多，而固定相电池还原的铁（III）最少，与铁的状态无关。贫铁细胞上清液每10（6）个细胞每小时最多可减少2 nmol Fe（III），而贫铁细胞上清液可减少0.5 nmol Fe（III），这意味着对分泌型还原剂的调节。一种这样的还原剂是3-羟基邻氨基苯甲酸（3HAA），其在贫铁培养物中的浓度高达29 microM，但在补充铁的培养物中的浓度小于2 microM。此外，当洗涤并重悬于低铁培养基中时，贫铁细胞分泌20.4 microM 3HAA，而贫铁细胞仅分泌4.5 microM 3HAA。每摩尔3HAA还原3摩尔Fe（III），增加3HAA浓度与增加上清液的还原活性相关。然而，3HAA仅占上清液还原活性的一半，表明存在其他还原剂。最后，我们发现黑色素化的固定相细胞每10（6）个细胞每h--16倍的非黑色素化细胞的速度降低了2 nmol的Fe（III）-暗示这种氧化还原聚合物参与了Fe（III）的还原。

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