Identification of the Elusive Pyruvate Reductase of Chlamydomonas reinhardtii Chloroplasts.
Identification of the Elusive Pyruvate Reductase of Chlamydomonas reinhardtii Chloroplasts.
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DOI：
10.1093/pcp/pcv167
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发表时间：
2016-01
影响因子：
4.9
通讯作者：
Nixon PJ
中科院分区：
文献类型：
--
作者：
Burgess SJ;Taha H;Yeoman JA;Iamshanova O;Chan KX;Boehm M;Behrends V;Bundy JG;Bialek W;Murray JW;Nixon PJ
在缺氧条件下，绿藻衣藻激活各种发酵途径，产生甲酸盐、乙酸盐、乙醇和少量其他代谢物，包括d-乳酸和氢。在确定参与这些途径的酶及其亚细胞位置方面已经取得了进展；然而，参与将丙酮酸还原为d-乳酸的酶的特性仍然不清楚。根据序列比较、酶活性测量、X射线结晶学、生化分级和敲除突变体的分析，我们得出结论：叶绿体中的丙酮酸还原是由由Cre07.g324550编码的依赖于NAD+的四聚体d-乳酸脱氢酶催化的。它在有氧生长过程中的表达支持了一种可能的功能，即将乳酸输出到线粒体，由依赖细胞色素的d-乳酸脱氢酶和乙醇酸脱氢酶氧化。我们还提出了一个修订的空间发酵模型，基于我们对细胞质中可能的丙酮酸脱羧酶PDC3的免疫化学检测。
Under anoxic conditions the green alga Chlamydomonas reinhardtii activates various fermentation pathways leading to the creation of formate, acetate, ethanol and small amounts of other metabolites including d-lactate and hydrogen. Progress has been made in identifying the enzymes involved in these pathways and their subcellular locations; however, the identity of the enzyme involved in reducing pyruvate to d-lactate has remained unclear. Based on sequence comparisons, enzyme activity measurements, X-ray crystallography, biochemical fractionation and analysis of knock-down mutants, we conclude that pyruvate reduction in the chloroplast is catalyzed by a tetrameric NAD+-dependent d-lactate dehydrogenase encoded by Cre07.g324550. Its expression during aerobic growth supports a possible function as a ‘lactate valve’ for the export of lactate to the mitochondrion for oxidation by cytochrome-dependent d-lactate dehydrogenases and by glycolate dehydrogenase. We also present a revised spatial model of fermentation based on our immunochemical detection of the likely pyruvate decarboxylase, PDC3, in the cytoplasm.