Importance of Glutamate Synthase in Glutamate Synthesis by Soybean Cell Suspension Cultures

The specific activities of glutamate synthase|EC 2.6.1.53, l-glutamine: alpha-ketoglutarate amino transferase (NADPH-oxidising)| and glutamine synthetase|EC 6.3.1.2, l-glutamate: ammonia ligase (ADP-forming)| extracted from soybean (Glycine max L.) cells grown in modified B5 medium were found to vary significantly in response to variations in the nitrogen content of the medium. The changes seen in specific activity levels could be correlated with similar patterns seen in the growth of the cells, in response to changes in the nitrogen content of the medium. By contrast, the specific activity of glutamate dehydrogenase|EC 1.4.1.2, l-glutamate: NAD(+) oxidoreductase (deaminating)|, was relatively low and invariant. Glutamate synthase was extracted from cells grown under optimal conditions, partially purified, and shown to have many properties in common with preparations of this enzyme extracted from other plant sources. Glutamate synthase was purified to homogeneity, using affinity chromatography on blue Sepharose.