Studies on the Enzymatic Synthesis of Glutamine

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Abstract
An improved method was described for obtaining from dried peas in highly purified form the enzyme catalyzing the synthesis of glutamine from glutamate and ammonia. The equilibrium constant for the overall reaction was determined and the enzyme characterized with respect to its affinities for the reactants. The glutamyl transfer reactions of this enzyme was further characterized. It is concluded that these transfer reactions and the arsenate-activated hydrolysis of glutamine are manifestations of the overall synthetic activity of the enzyme. The mechanism of the synthesis reaction was studied by means of the enzyme-catalyzed exchange of radioactive orthophosphate and adenosine diphosphate (ADP) into adenosine triphosphate (ATP). The existence of a glutamate-ATP-enzyme complex as an intermediate is indicated and it is suggested that this intermediate is common to the glutamine synthesis reaction and the glutamyl transfer reactions.