Guo Jiantao, Frost J W
Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, USA.
J Am Chem Soc. 2002 Jan 30;124(4):528-9. doi: 10.1021/ja016963v.
With respect to the source of the nitrogen atom incorporated into the aminoshikimate pathway, d-erythrose 4-phosphate has been proposed to undergo a transamination reaction resulting in formation of 1-deoxy-1-imino-d-erythrose 4-phosphate. Condensation of this metabolite with phosphoenolpyruvate catalyzed by aminoDAHP synthase would then hypothetically form the 4-amino-3,4-dideoxy-d-arabino-heptulosonic acid 7-phosphate (aminoDAHP), which is the first committed intermediate of the aminoshikimate pathway. However, in vitro formation of aminoDAHP has not been observed. In this account, the possibility is examined that 3-amino-3-deoxy-d-fructose 6-phosphate is the source of the nitrogen atom of the aminoshikimate pathway. Transketolase-catalyzed ketol transfer from 3-amino-3-deoxy-d-fructose 6-phosphate to d-ribose 5-phosphate would hypothetically release 1-deoxy-1-imino-d-erythrose 4-phosphate. Along these lines, a chemoenzymatic synthesis of 3-amino-3-deoxy-d-fructose 6-phosphate was elaborated. Incubation of 3-amino-3-deoxy-d-fructose 6-phosphate in Amycolatopsis mediterranei crude cell lysate with d-ribose 5-phosphate and phosphoenolpyruvate resulted in the formation of aminoDAHP and 3-amino-5-hydroxybenzoic acid. 3-[15N]-Amino-3-deoxy-d-6,6-[2H2]-fructose 6-phosphate was also synthesized and similarly incubated in A. mediterranei crude cell lysate. Retention of both 15N and 2H2 labeling in product aminoDAHP indicates that 3-amino-3-deoxy-d-fructose 6-phosphate is serving as a sequestered form of 1-deoxy-1-imino-d-erythrose 4-phosphate.
关于并入氨基莽草酸途径的氮原子来源，有人提出磷酸d - 赤藓糖4 - 磷酸会发生转氨反应，生成1 - 脱氧 - 1 - 亚氨基 - d - 赤藓糖4 - 磷酸。由氨基DAHP合酶催化该代谢物与磷酸烯醇丙酮酸缩合，理论上会形成7 - 磷酸 - 4 - 氨基 - 3,4 - 二脱氧 - d - 阿拉伯 - 庚酮糖酸（氨基DAHP），它是氨基莽草酸途径的第一个关键中间体。然而，尚未观察到氨基DAHP的体外形成。在此，研究了6 - 磷酸 - 3 - 氨基 - 3 - 脱氧 - d - 果糖作为氨基莽草酸途径氮原子来源的可能性。理论上，转酮醇酶催化的酮醇从6 - 磷酸 - 3 - 氨基 - 3 - 脱氧 - d - 果糖转移到5 - 磷酸 - d - 核糖上会释放出1 - 脱氧 - 1 - 亚氨基 - d - 赤藓糖4 - 磷酸。按照这些思路，详细阐述了6 - 磷酸 - 3 - 氨基 - 3 - 脱氧 - d - 果糖的化学酶促合成。将6 - 磷酸 - 3 - 氨基 - 3 - 脱氧 - d - 果糖与5 - 磷酸 - d - 核糖和磷酸烯醇丙酮酸在地中海拟无枝酸菌粗细胞裂解物中孵育，结果生成了氨基DAHP和3 - 氨基 - 5 - 羟基苯甲酸。还合成了3 - [¹⁵N] - 氨基 - 3 - 脱氧 - d - 6,6 - [²H₂] - 果糖6 - 磷酸，并在地中海拟无枝酸菌粗细胞裂解物中进行类似孵育。产物氨基DAHP中¹⁵N和²H₂标记的保留表明6 - 磷酸 - 3 - 氨基 - 3 - 脱氧 - d - 果糖作为1 - 脱氧 - 1 - 亚氨基 - d - 赤藓糖4 - 磷酸的一种隐蔽形式起作用。
