Purification of three aminotransferases from Hydrogenobacter thermophilus TK-6-novel types of alanine or glycine aminotransferase
Purification of three aminotransferases from Hydrogenobacter thermophilus TK-6-novel types of alanine or glycine aminotransferase
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DOI：
10.1111/j.1742-4658.2010.07604.x
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发表时间：
2010-04-01
期刊：
影响因子：
5.4
通讯作者：
Igarashi, Yasuo
中科院分区：
文献类型：
--
作者：
Kameya, Masafumi;Arai, Hiroyuki;Igarashi, Yasuo
氨基转移酶催化氨基酸的合成和降解反应，并且在大多数生物体中充当中心碳和氮代谢之间的关键连接。本研究从嗜热氢杆菌（Hydrogenophilus thermophilus）中分离纯化了三种氨基转移酶（AT 1、AT 2和AT 3），并对其进行了表征。AT1、AT2和AT3分别表现出谷氨酸：草酰乙酸转氨酶、谷氨酸：丙酮酸转氨酶和丙氨酸：乙醛酸转氨酶活性。此外，AT 1和AT 2都催化谷氨酸：乙醛酸氨基转移酶反应。有趣的是，系统发育分析表明，AT2属于转氨酶家族IV，而已知的谷氨酸：丙酮酸转氨酶和谷氨酸：乙醛酸转氨酶是家族I γ的成员。与此相反，AT3被归类为家族I，远离真核丙氨酸：乙醛酸氨基转移酶属于家族IV。虽然滨海热球菌丙氨酸：乙醛酸氨基转移酶是家族I丙氨酸：乙醛酸氨基转移酶的唯一已知实例，但表明该丙氨酸：乙醛酸氨基转移酶和AT 3源自家族I内的不同谱系，因为这两种酶既不具有高序列相似性，也不具有推定的底物结合残基。据我们所知，这项研究是细菌谷氨酸：乙醛酸转氨酶和丙氨酸：乙醛酸转氨酶的一级结构的第一份报告，并证明了存在的新类型的转氨酶与已知的真核生物和古细菌同工酶在遗传学上不同。
Aminotransferases catalyse synthetic and degradative reactions of amino acids, and serve as a key linkage between central carbon and nitrogen metabolism in most organisms. In this study, three aminotransferases (AT1, AT2 and AT3) were purified and characterized from Hydrogenobacter thermophilus, a hydrogen-oxidizing chemolithoautotrophic bacterium, which has been reported to possess unique features in its carbon and nitrogen anabolism. AT1, AT2 and AT3 exhibited glutamate:oxaloacetate aminotransferase, glutamate:pyruvate aminotransferase and alanine:glyoxylate aminotransferase activities, respectively. In addition, both AT1 and AT2 catalysed a glutamate:glyoxylate aminotransferase reaction. Interestingly, phylogenetic analysis showed that AT2 belongs to aminotransferase family IV, whereas known glutamate:pyruvate aminotransferases and glutamate:glyoxylate aminotransferases are members of family I gamma. In contrast, AT3 was classified into family I, distant from eukaryotic alanine:glyoxylate aminotransferases which belong to family IV. Although Thermococcus litoralis alanine:glyoxylate aminotransferase is the sole known example of family I alanine:glyoxylate aminotransferases, it is indicated that this alanine:glyoxylate aminotransferase and AT3 are derived from distinct lineages within family I, because neither high sequence similarity nor putative substrate-binding residues are shared by these two enzymes. To our knowledge, this study is the first report of the primary structure of bacterial glutamate:glyoxylate aminotransferase and alanine:glyoxylate aminotransferase, and demonstrates the presence of novel types of aminotransferase phylogenetically distinct from known eukaryotic and archaeal isozymes.