Antoniuk L P
Prikl Biokhim Mikrobiol. 2007 May-Jun;43(3):272-8.
Data on Glutamine synthetase (GS) of Azospirillum brasilense, a rhizobacterium stimulating plant growth, have been reviewed. GS of the azospirillum is a type alpha12 dodecamer with oligomer and monomer having molecular weights of 630 and 52 kDa, respectively. Glutamine synthesis is performed in 12 active sites of the enzyme, depending, first and foremost, on the extent of GS adenylation and, secondarily, on the exact bivalent metal cations involved in the catalysis. Structural characteristics and catalytic properties of the completely unadenylated and moderately adenylated forms of GS of A. brasilense have been studied. The enzyme appears as a highly structured protein, with alpha helices and beta structures accounting for about 70% of the polypeptide chain length. Binding of Mg2+, Co2+, and Mn2+ to the protein globule changes both the secondary structure and the catalytic properties of the enzyme. The uses of nuclear gamma resonance emission spectroscopy demonstrates that the active center of GS of the azospirillum has two metal-binding sites differing in their affinity for Co2+. The activity and biosynthesis of GS of the azospirillum is regulated by wheat lectin (a molecular signal of the host plant), in addition to other means of regulation described for GSs.
对促进植物生长的根际细菌巴西固氮螺菌谷氨酰胺合成酶（GS）的数据进行了综述。该固氮螺菌的GS是一种α12型十二聚体，其寡聚体和单体的分子量分别为630 kDa和52 kDa。谷氨酰胺的合成在该酶的12个活性位点进行，首先主要取决于GS腺苷酸化的程度，其次取决于参与催化的确切二价金属阳离子。对巴西固氮螺菌GS完全未腺苷酸化和适度腺苷酸化形式的结构特征和催化特性进行了研究。该酶表现为一种高度结构化的蛋白质，α螺旋和β结构约占多肽链长度的70%。Mg2+、Co2+和Mn2+与蛋白质球体的结合会改变酶的二级结构和催化特性。核γ共振发射光谱的应用表明，固氮螺菌GS的活性中心有两个对Co2+亲和力不同的金属结合位点。除了已描述的GS的其他调控方式外，巴西固氮螺菌GS的活性和生物合成还受小麦凝集素（宿主植物的分子信号）调控。
