精胺合成酶是一种氨基丙基转移酶,它将氨基丙基添加到必需的多胺亚精胺中,形成四胺精胺,人类正常神经发育所需要的,植物抗盐和抗旱性,和酵母CoA生物合成。我们首次在功能上鉴定了细菌精胺合成酶,来源于门芽孢杆菌,Rhodothermota,热脱硫细菌,Nitrosirota,Deinococcota和Pseudomonadota。我们还鉴定了合成精胺相同质量异构体热精胺的细菌氨丙基转移酶,来自于门蓝细菌,热脱硫细菌,Nitrosirota,网虫,Armatimonadota和Pseudomonadota,包括人类机会致病菌铜绿假单胞菌。这些细菌合酶中的大多数能够从二胺腐胺中合成精胺或热精胺,因此也具有亚精胺合成酶活性。我们发现大多数热精胺合成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成酶。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,证明它们是潜在的去甲亚精胺合成酶。在鉴定出的18种细菌亚精胺合成酶中,17能够氨基丙基胍丁胺形成N1-氨基丙基胍丁胺,包括枯草芽孢杆菌的亚精胺合成酶,一种已知缺乏腐胺的物种。这表明亚精胺生物合成的N1-氨基丙基胍丁胺途径,绕过腐胺,在编码L-精氨酸脱羧酶的物种中,亚精胺生物合成的默认途径可能比实现的广泛得多,并且可能是用于生产胍丁胺的默认途径。一些热精胺合成酶能够氨基丙基化N1-氨基丙基胍丁胺以形成N12-胍热精胺。我们的研究揭示了细菌多胺生物合成的意外多样化,并表明胍丁胺的作用更为突出。
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 Pseudomonas aeruginosa. 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 N1-aminopropylagmatine, including the spermidine synthase of Bacillus subtilis, a species known to be devoid of putrescine. This suggests that the N1-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 N1-aminopropylagmatine to form N12-guanidinothermospermine. Our study reveals an unsuspected diversification of bacterial polyamine biosynthesis and suggests a more prominent role for agmatine.