Vichido I, Mora Y, Quinto C, Palacios R, Mora J
J Gen Microbiol. 1978 Jun;106(2):251-9. doi: 10.1099/00221287-106-2-251.
A higher activity of glutamine synthetase (EC 6.3.1.2) was found in Neurospora crassa when NH4+ was limiting as nitrogen source than when glutamate was limiting. When glutamate, glutamine or NH4+ were in excess, a lower activity was found. Immunological titration and sucrose gradient sedimentation of the enzyme established that under all these conditions enzyme activity corresponded to enzyme concentration and that the octamer was the predominant oligomeric form. When N. crassa was shifted from nitrogen-limiting substrates to excess product as nitrogen source, the concentration of glutamine synthetase was adjusted with kinetics that closely followed dilution by growth. When grown on limiting amounts of glutamate, a lower oligomer was present in addition to the octameric form of the enzyme. When the culture was shifted to excess NH4+, glutamine accululated at a high rate; nevertheless, there was only a slow decrease in enzyme activity and no modification of the oligomeric pattern.
当以NH₄⁺作为氮源受到限制时，在粗糙脉孢菌中发现谷氨酰胺合成酶（EC 6.3.1.2）的活性高于以谷氨酸作为氮源受到限制时。当谷氨酸、谷氨酰胺或NH₄⁺过量时，发现活性较低。通过对该酶的免疫滴定和蔗糖梯度沉降确定，在所有这些条件下酶活性与酶浓度相对应，并且八聚体是主要的寡聚形式。当粗糙脉孢菌从限制氮的底物转移到作为氮源的过量产物时，谷氨酰胺合成酶的浓度通过与生长稀释密切相关的动力学进行调节。当在有限量的谷氨酸上生长时，除了酶的八聚体形式外还存在较低的寡聚体。当培养物转移到过量的NH₄⁺时，谷氨酰胺以高速率积累；然而，酶活性仅缓慢下降，并且寡聚模式没有改变。
