Glutamine synthetase GS is a key enzyme in nitrogen assimilation and metabolism. It plays a crucial role in the conversion of inorganic nitrogen ammonia into organic nitrogen-containing compounds, such as amino acids, which are essential for the synthesis of proteins, nucleic acids, and other biomolecules in living organisms.The primary function of glutamine synthetase is to catalyze the conversion of glutamate and ammonia into glutamine. This reaction is important for detoxifying ammonia, which is toxic to cells, and incorporating it into organic molecules that can be used by the cell. The reaction proceeds in two steps:1. Activation of glutamate: In the first step, glutamine synthetase catalyzes the ATP-dependent phosphorylation of the carboxyl group of glutamate, forming an intermediate called -glutamyl phosphate and releasing ADP. This step activates the glutamate molecule for the subsequent reaction with ammonia.2. Ammonia incorporation: In the second step, the enzyme facilitates the nucleophilic attack of ammonia on the -glutamyl phosphate intermediate, resulting in the formation of glutamine and inorganic phosphate Pi . This step incorporates the ammonia molecule into the glutamate, forming glutamine.The overall reaction can be summarized as follows:Glutamate + ATP + NH3 Glutamine + ADP + PiGlutamine synthetase is regulated by several mechanisms, including feedback inhibition, covalent modification, and gene expression, to ensure that the appropriate levels of glutamine are maintained within the cell. This regulation is essential for maintaining nitrogen homeostasis and coordinating nitrogen metabolism with other cellular processes.In summary, glutamine synthetase plays a critical role in nitrogen assimilation and metabolism by catalyzing the conversion of glutamate and ammonia into glutamine. This enzyme helps to detoxify ammonia and incorporate it into organic molecules, which are essential for the synthesis of proteins, nucleic acids, and other biomolecules in living organisms.