Samasil Khanittha, Lopes de Carvalho Leonor, Mäenpää Pirkko, Salminen Tiina A, Incharoensakdi Aran
Department of Biochemistry, Faculty of Science, Chulalongkorn University, Bangkok, Thailand; Structural Bioinformatics Laboratory, Biochemistry, Faculty of Science and Engineering, Åbo Akademi University, FI20520 Turku, Finland.
Structural Bioinformatics Laboratory, Biochemistry, Faculty of Science and Engineering, Åbo Akademi University, FI20520 Turku, Finland.
Plant Physiol Biochem. 2017 Oct;119:159-169. doi: 10.1016/j.plaphy.2017.08.018. Epub 2017 Aug 26.
The intracellular polyamine contents are regulated not only by polyamine biosynthesis and transport but also by polyamine degradation catalyzed by copper-dependent amine oxidase (DAO) and FAD-dependent polyamine oxidase (PAO). The genome sequence of Synechocystis sp. PCC 6803 reveals the presence of at least one putative polyamine oxidase gene, slr5093. The open reading frame of slr5093 encoding Synechocystis polyamine oxidase (SynPAO, E.C. 1.5.3.17) was expressed in Escherichia coli. The purified recombinant enzyme had the characteristic absorption spectrum of a flavoprotein with absorbance peaks at 380 and 450 nm. The optimum pH and temperature for the oxidation of both spermidine and spermine are 8.5 and 30 °C, respectively. The enzyme catalyzed the conversion of spermine and spermidine to spermidine and putrescine, respectively, with higher catalytic efficiency when spermine served as substrate. These results suggest that SynPAO is a polyamine oxidase involved in a polyamine back-conversion pathway. Based on the structural analysis, Gln94, Tyr403 and Thr440 in SynPAO are predicted to be important residues in the active site.
细胞内多胺含量不仅受多胺生物合成和转运的调节，还受铜依赖性胺氧化酶（DAO）和黄素腺嘌呤二核苷酸依赖性多胺氧化酶（PAO）催化的多胺降解的调节。聚球藻属PCC 6803的基因组序列显示存在至少一个假定的多胺氧化酶基因，即slr5093。编码聚球藻多胺氧化酶（SynPAO，E.C. 1.5.3.17）的slr5093的开放阅读框在大肠杆菌中表达。纯化的重组酶具有黄素蛋白的特征吸收光谱，在380和450nm处有吸收峰。亚精胺和精胺氧化的最适pH和温度分别为8.5和30℃。该酶分别催化精胺和亚精胺转化为亚精胺和腐胺，以精胺为底物时催化效率更高。这些结果表明SynPAO是参与多胺逆向转化途径的多胺氧化酶。基于结构分析，预测SynPAO中的Gln94、Tyr403和Thr440是活性位点中的重要残基。
