Highly-expressed polyamine oxidases catalyze polyamine back conversion in Brachypodium distachyon
Highly-expressed polyamine oxidases catalyze polyamine back conversion in Brachypodium distachyon
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DOI：
10.1007/s10265-017-0989-2
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发表时间：
2017-10
影响因子：
2.8
通讯作者：
Yoshihiro Takahashi;K. Ono;Yuuta Akamine;T. Asano;Masatoshi Ezaki;Itsupei Mouri
中科院分区：
文献类型：
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作者：
Yoshihiro Takahashi;K. Ono;Yuuta Akamine;T. Asano;Masatoshi Ezaki;Itsupei Mouri
为了了解二穗短柄草中的多胺（PA）分解代谢途径，我们重点研究了含黄素的多胺氧化酶（PAO），并在分子和生化水平上对其进行了表征。通过数据库搜索鉴定出五个 PAO 亚型，我们将它们命名为 BdPAO1 至 BdPAO5。通过对地上组织（如叶、茎和花序）进行基因表达分析，发现正常生长条件下，BdPAO2是最丰富的PAO基因，其次是BdPAO3和BdPAO4。 BdPAO1和BdPAO5的表达水平非常低。与 BdPAO2、BdPAO3 和 BdPAO4 属于同一进化枝的所有拟南芥和水稻直向同源物在其 C 末端都具有保守的过氧化物酶体靶向信号序列。 BdPAO2和BdPAO4的氨基酸序列也显示出这样的序列，但BdPAO3没有。我们选择表达水平最高的基因 (BdPAO2) 和缺乏 PAO 的过氧化物酶体靶向信号 (BdPAO3) 进行底物特异性和分解代谢途径的生化分析。 BdPAO2 催化精胺 (Spm) 或热精胺转化为亚精胺 (Spd)，以及 Spd 转化为腐胺，但其最有利的底物是 Spd。相比之下，BdPAO3 有利于 Spm 作为底物并催化四胺转化为 Spd。这些结果表明，B 中的主要 PAO。二穗花具有反向转换活性。
To understand the polyamine (PA) catabolic pathways inBrachypodium distachyon, we focused on the flavin-containing polyamine oxidase enzymes (PAO), and characterized them at the molecular and biochemical levels. FivePAOisoforms were identified from database searches, and we named them BdPAO1 to BdPAO5. By gene expression analysis using above-ground tissues such as leaf, stem and inflorescence, it was revealed thatBdPAO2is the most abundant PAO gene in normal growth conditions, followed byBdPAO3andBdPAO4. BdPAO1andBdPAO5were expressed at very low levels. AllArabidopsis thalianaand rice orthologs belonging to the same clade as BdPAO2, BdPAO3 and BdPAO4 have conserved peroxisome-targeting signal sequences at their C-termini. Amino acid sequences of BdPAO2 and BdPAO4 also showed such a sequence, but BdPAO3 did not. We selected the gene with the highest expression level (BdPAO2) and the peroxisome-targeting signal lacking PAO (BdPAO3) for biochemical analysis of substrate specificity and catabolic pathways. BdPAO2 catalyzed conversion of spermine (Spm) or thermospermine to spermidine (Spd), and Spd to putrescine, but its most-favored substrate was Spd. In contrast, BdPAO3 favored Spm as substrate and catalyzed conversion of tetraamines to Spd. These results indicated that the major PAOs inB. distachyonhave back-conversion activity.