Glutamine Synthetase from Pseudomonas syringae pv. tabaci: Properties and Inhibition by Tabtoxinine-β-lactam
Glutamine Synthetase from Pseudomonas syringae pv. tabaci: Properties and Inhibition by Tabtoxinine-β-lactam
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烟粉假单胞菌谷氨酰胺合成酶：特性和 Tabtoxinine-β-内酰胺的抑制作用
DOI：
10.1099/00221287-131-5-1061
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发表时间：
1985
期刊：
影响因子：
1.5
通讯作者：
R. Durbin
中科院分区：
文献类型：
--
作者：
Michael D. Thomas;R. Durbin
来自丁香假单胞菌 pv. 的谷氨酰胺合成酶。烟粉虱纯化了 500 倍。使用 10 mM-谷氨酸、20mM-ATP 和 4mM-NH4Cl 观察到最大活性。该酶表现出底物抑制作用；谷氨酸、镁含量较高。 ATP 或 NH4Cl 降低其活性。 γ-谷氨酰转移酶活性被 Mg2+ 抑制（10mM-Mg2+ 时抑制 75%）。该酶是热稳定的并且似乎仅存在一种形式。 Tabtoxinine-β-lactam，pv 产生的 tabtoxin 的水解产物。烟粉虱，使酶失活。这种抑制与抑制剂的浓度呈线性关系，并且酶活性不能通过透析、丙酮沉淀或与粗制细胞裂解液一起孵育来恢复。镁。抑制剂的结合需要 ATP 和铵离子：在两种 Mg 存在的情况下，将 tabtoxinine-β-内酰胺与酶一起孵育。与单独孵育或单独孵育相比，ATP 和铵离子导致合成酶活性下降幅度更大。如果在测定中使用 ADP，则 Tabtoxinine-β-内酰胺不会抑制该酶的 γ-谷氨酰转移酶活性，但在使用 ATP 时会抑制该酶的活性。
Glutamine synthetase from Pseudomonas syringae pv. tabaci was purified 500-fold. Maximum activity was observed with 10 mM-glutamate, 20mM-ATP and 4mM-NH4Cl. The enzyme exhibited substrate inhibition; higher levels of glutamate, Mg. ATP or NH4Cl decreased its activity. The γ-glutamyltransferase activity was inhibited by Mg2+ (75% at 10mM-Mg2+). The enzyme was heat stable and there appeared to be only one form present. Tabtoxinine-β-lactam, a hydrolytic product of tabtoxin produced by pv. tabaci, inactivated the enzyme. This inhibition was linear with respect to the concentration of the inhibitor, and enzyme activity could not be recovered by dialysis, acetone precipitation or incubation with crude cell lysate. Mg. ATP and ammonium ions were required for binding of the inhibitor: incubation of tabtoxinine-β-lactam with the enzyme in the presence of both Mg. ATP and ammonium ions resulted in a greater decrease in synthetase activity than incubation with either one or neither component. Tabtoxinine-β-lactam did not inhibit the y-glutamyltransferase activity of the enzyme if ADP was used in the assay, but did when ATP was used.