Nakamura K, Stadtman E R
Proc Natl Acad Sci U S A. 1984 Apr;81(7):2011-5. doi: 10.1073/pnas.81.7.2011.
Escherichia coli glutamine synthetase (GS) was inactivated by a nonenzymic mixed-function oxidation system composed of ascorbate, O2, and Fe(III). Partial inactivation of GS by this system leads to the formation of hybrid GS molecules (dodecamers) composed of both active and inactive subunits. Subunit interactions in these hybrid molecules are weaker than in the native enzyme, as indicated by the kinetics of subunit dissociation in the presence of 4 M urea. Heterologous subunit interactions in these hybrid molecules do not affect the affinity of active subunits for glutamate. Incubation of partially adenylylated GS preparations (n = 6.7) with the ascorbate system in the absence of substrates leads to preferential oxidative inactivation of unadenylylated subunits, whereas incubation in the presence of ATP and glutamate leads to preferential inactivation of adenylylated subunits.
大肠杆菌谷氨酰胺合成酶（GS）被由抗坏血酸盐、O₂和Fe(III)组成的非酶混合功能氧化系统失活。该系统对GS的部分失活导致形成由活性和非活性亚基组成的杂合GS分子（十二聚体）。如在4M尿素存在下亚基解离动力学所示，这些杂合分子中的亚基相互作用比天然酶中的弱。这些杂合分子中的异源亚基相互作用不影响活性亚基对谷氨酸的亲和力。在无底物的情况下，将部分腺苷酸化的GS制剂（n = 6.7）与抗坏血酸盐系统一起孵育会导致未腺苷酸化亚基优先发生氧化失活，而在ATP和谷氨酸存在下孵育会导致腺苷酸化亚基优先失活。
