Contributions of the Peroxisome and β-Oxidation Cycle to Biotin Synthesis in Fungi
Contributions of the Peroxisome and β-Oxidation Cycle to Biotin Synthesis in Fungi
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DOI：
10.1074/jbc.m111.279687
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发表时间：
2011-12-09
影响因子：
4.8
通讯作者：
Poirier, Yves
中科院分区：
文献类型：
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作者：
Magliano, Pasqualina;Flipphi, Michel;Poirier, Yves
D-生物素双环合成的第一步是由8-氨基-7-氧酮酸(AON)合成酶催化L-丙氨酸和戊二酸硫酯的脱羧基缩合反应。我们发现，由生物F基因编码的Nidulans Aon合成酶是一种带有1型过氧化物体靶向序列(PTS1)的过氧化物体酶。由于编码PTS1受体的胞质Aon变异体的表达或pexE的缺失，使得A.nidulans成为生物素营养缺陷体，因此Aon定位于过氧化体是生物素合成所必需的。AON合成酶与PTS1在整个真菌王国中广泛存在，存在于子囊菌、担子菌和基础真菌谱系中，但不存在于酵母种复合体的代表中，包括酿酒酵母。在缺乏生物素的条件下，缺失AoxA或FoxA多功能蛋白的突变株菌落生长速率显著下降，而在添加槟榔酸的条件下，菌落生长部分恢复。这些结果表明，Pimeloyl-CoA是Aon合成酶的体内底物，它是在弧菌中通过β-氧化循环在过氧化体中产生的，可能在广泛的真菌中也是如此。然而，在酿酒酵母或大肠杆菌中，β-氧化循环并不是生物素合成所必需的。这些结果表明，细菌和真核生物中存在合成戊二酸酯中间体的替代途径，而酵母菌使用的途径不同于大多数真菌使用的途径。
The first step in the synthesis of the bicyclic rings of D-biotin is mediated by 8-amino-7-oxononanoate (AON) synthase, which catalyzes the decarboxylative condensation of L-alanine and pimelate thioester. We found that the Aspergillus nidulans AON synthase, encoded by the bioF gene, is a peroxisomal enzyme with a type 1 peroxisomal targeting sequence (PTS1). Localization of AON to the peroxisome was essential for biotin synthesis because expression of a cytosolic AON variant or deletion of pexE, encoding the PTS1 receptor, rendered A. nidulans a biotin auxotroph. AON synthases with PTS1 are found throughout the fungal kingdom, in ascomycetes, basidiomycetes, and members of basal fungal lineages but not in representatives of the Saccharomyces species complex, including Saccharomyces cerevisiae. A. nidulans mutants defective in the peroxisomal acyl-CoA oxidase AoxA or the multifunctional protein FoxA showed a strong decrease in colonial growth rate in biotin-deficient medium, whereas partial growth recovery occurred with pimelic acid supplementation. These results indicate that pimeloyl-CoA is the in vivo substrate of AON synthase and that it is generated in the peroxisome via the beta-oxidation cycle in A. nidulans and probably in a broad range of fungi. However, the beta-oxidation cycle is not essential for biotin synthesis in S. cerevisiae or Escherichia coli. These results suggest that alternative pathways for synthesis of the pimelate intermediate exist in bacteria and eukaryotes and that Saccharomyces species use a pathway different from that used by the majority of fungi.