Unkefer C J, London R E, Durbin R D, Uchytil T F, Langston-Unkefer P J
J Biol Chem. 1987 Apr 15;262(11):4994-9.
Tabtoxinine-beta-lactam, an irreversible inhibitor of glutamine synthetase is produced by several pathovars of Pseudomonas syringae. We have examined tabtoxinine-beta-lactam biosynthesis, an important and poorly characterized step in pathogenesis caused by this organism. We have identified the biosynthetic precursors of tabtoxinine-beta-lactam by incorporating 13C from specifically 13C-labeled D-glucose precursors and determining the labeling pattern using 13C NMR spectroscopy. Tabtoxinine-beta-lactam is generated by combining a 4-carbon fragment, a 2-carbon fragment, and a single carbon. The 4-carbon fragment arises from aspartic acid, and the 2-carbon unit is donated from carbons 2 and 3 of pyruvate. The 6-carbon backbone of tabtoxinine-beta-lactam arises from the condensation of fragments from aspartate and pyruvate, probably using reactions analogous to the initial steps in the pathway of lysine biosynthesis.
丁香假单胞菌的几个致病型会产生β-内酰胺基tabtoxinine，它是谷氨酰胺合成酶的不可逆抑制剂。我们研究了β-内酰胺基tabtoxinine的生物合成过程，这是该生物体致病过程中一个重要但了解甚少的步骤。我们通过掺入来自特定13C标记的D-葡萄糖前体的13C，并使用13C核磁共振光谱确定标记模式，从而鉴定出了β-内酰胺基tabtoxinine的生物合成前体。β-内酰胺基tabtoxinine是由一个4碳片段、一个2碳片段和一个单碳结合而成的。4碳片段来自天冬氨酸，2碳单元由丙酮酸的2号和3号碳提供。β-内酰胺基tabtoxinine的6碳主链源于天冬氨酸和丙酮酸片段的缩合，可能使用了类似于赖氨酸生物合成途径初始步骤的反应。
