THE ENERGETICS OF EXTRACELLULAR FE(III) REDUCTION BY IRON‐LIMITED CHLAMYDOMONAS REINHARDTII (CHLOROPHYTA)
THE ENERGETICS OF EXTRACELLULAR FE(III) REDUCTION BY IRON‐LIMITED CHLAMYDOMONAS REINHARDTII (CHLOROPHYTA)
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限铁莱茵衣藻（绿藻）减少细胞外 FE(III) 的能量
DOI：
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发表时间：
1998
期刊：
影响因子：
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通讯作者：
H. Weger
中科院分区：
文献类型：
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作者：
X. Xue;Christopher M. Collins;H. Weger
当以铁氰化物或Fe（III）-EDTA形式提供Fe（III）时，绿色莱茵衣藻的Fe限制细胞（Fe限制生长速率= 0.3 d−1）将细胞外Fe（III）还原为Fe（II）; Fe（III）还原受光刺激。在黑暗和光合作用过程中，铁氰化物的减少伴随着细胞NADPH水平的下降，伴随着NADP+的增加。在铁氰化物还原过程中，NADH和NAD+水平没有明显改变。此外，在铁氰化物还原过程中，细胞内单磷酸己糖水平下降，6-磷酸葡萄糖酸盐水平增加。大多数糖酵解和三羧酸循环中间产物的水平基本不变。铁氰化物的减少也与细胞ATP水平的降低，ADP和AMP的伴随增加，以及细胞外酸化的增加有关。酸化对H+-ATP酶抑制剂N，N′-二环己基碳二亚胺（DCCD）的抑制敏感。我们的结论是，氧化戊糖磷酸途径提供还原当量的Fe（III）还原在黑暗中，也有助于还原当量的Fe（III）还原在光合作用。ATP的下降可能是由于铁氰化物还原过程中质膜H+-ATP酶的激活，与还原当量的提供没有直接关系。
Fe‐limited cells of the green alga Chlamydomonas reinhardtii (Fe‐limited growth rate = 0.3 d−1) reduced extracellular Fe(III) to Fe(II) when Fe(III) was supplied as ferricyanide or Fe(III)‐EDTA; Fe(III) reduction was stimulated by light. In both darkness and during photosynthesis, ferricyanide reduction was accompanied by a decrease in cellular NADPH levels, with a concomitant increase in NADP+. NADH and NAD+ levels were not measurably altered during ferricyanide reduction. Furthermore, cellular hexose monophosphate levels declined and 6‐phosphogluconate levels increased during ferricyanide reduction. Levels of most glycolytic and tricarboxylic acid cycle intermediates were mostly unaltered. Ferricyanide reduction was also associated with a decrease in cellular ATP levels, a concomitant increase in ADP and AMP, and increased extracellular acidification. The acidification was sensitive to inhibition by the H+‐ATPase inhibitor N,N′‐dicyclohexylcarbodiimide (DCCD). We conclude that the oxidative pentose phosphate pathway provides reducing equivalents for Fe(III) reduction in darkness and also contributes reducing equivalents to Fe(III) reduction during photosynthesis. The decline in ATP was likely due to activation of the plasma membrane H+‐ATPase during ferricyanide reduction and was not directly associated with provision of reducing equivalents.