Spermine synthase is an aminopropyltransferase that adds an aminopropyl group to the essential polyamine spermidine to form tetraamine spermine, needed for normal human neural development, plant salt and drought resistance, and yeast CoA biosynthesis. We functionally identify for the first time bacterial spermine synthases, derived from phyla Bacillota, Rhodothermota, Thermodesulfobacteriota, Nitrospirota, Deinococcota, and Pseudomonadota. We also identify bacterial aminopropyltransferases that synthesize the spermine same mass isomer thermospermine, from phyla Cyanobacteriota, Thermodesulfobacteriota, Nitrospirota, Dictyoglomota, Armatimonadota, and Pseudomonadota, including the human opportunistic pathogen . Most of these bacterial synthases were capable of synthesizing spermine or thermospermine from the diamine putrescine and so possess also spermidine synthase activity. We found that most thermospermine synthases could synthesize tetraamine norspermine from triamine norspermidine, that is, they are potential norspermine synthases. This finding could explain the enigmatic source of norspermine in bacteria. Some of the thermospermine synthases could synthesize norspermidine from diamine 1,3-diaminopropane, demonstrating that they are potential norspermidine synthases. Of 18 bacterial spermidine synthases identified, 17 were able to aminopropylate agmatine to form -aminopropylagmatine, including the spermidine synthase of , a species known to be devoid of putrescine. This suggests that the -aminopropylagmatine pathway for spermidine biosynthesis, which bypasses putrescine, may be far more widespread than realized and may be the default pathway for spermidine biosynthesis in species encoding L-arginine decarboxylase for agmatine production. Some thermospermine synthases were able to aminopropylate -aminopropylagmatine to form -guanidinothermospermine. Our study reveals an unsuspected diversification of bacterial polyamine biosynthesis and suggests a more prominent role for agmatine.

中文翻译：

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细菌精胺、热精胺、去甲精胺、去甲亚精胺、亚精胺和 N1-氨丙基胍丁胺合酶的功能鉴定


精胺合酶是一种氨丙基转移酶，可将氨丙基添加到必需的多胺亚精胺上，形成四胺精胺，这是人类正常神经发育、植物抗盐和干旱以及酵母 CoA 生物合成所需的。我们首次在功能上鉴定了源自芽孢杆菌门、红恒温菌门、热脱磺菌门、硝化螺菌门、奇球菌门和假单胞菌门的细菌精胺合酶。我们还鉴定了细菌氨丙基转移酶，其合成精胺相同质量异构体热精胺，来自蓝细菌门、热脱硫细菌门、硝化螺菌门、网球菌门、犰狳单胞菌门和假单胞菌门，包括人类机会性病原体。大多数这些细菌合酶能够从二胺腐胺合成精胺或热精胺，因此也具有亚精胺合酶活性。我们发现大多数热精胺合酶可以从三胺去甲亚精胺合成四胺去甲精胺，即它们是潜在的去甲精胺合酶。这一发现可以解释细菌中去甲精胺的神秘来源。一些热精胺合酶可以从二胺1,3-二氨基丙烷合成去甲亚精胺，表明它们是潜在的去甲亚精胺合酶。在已鉴定的 18 种细菌亚精胺合酶中，有 17 种能够将胍丁胺氨丙基化形成 γ-氨丙基胍丁胺，其中包括已知不含腐胺的物种的亚精胺合酶。这表明，绕过腐胺的亚精胺生物合成的β-氨基丙基胍丁胺途径可能比我们想象的要广泛得多，并且可能是编码用于胍丁胺生产的L-精氨酸脱羧酶的物种中亚精胺生物合成的默认途径。 一些热精精胺合酶能够氨丙基化-氨丙基胍丁胺以形成-胍基热精精胺。我们的研究揭示了细菌多胺生物合成的意想不到的多样化，并表明胍丁胺的作用更为突出。