The optimum pH of glutamine synthetase varied with the type and concentration of divalent cation present : pH 7.0-8.0 with 30mM Mg²⁺, 6.0-7.0 with 30mM Mn²⁺ and 7.0-8.0 with 4mM Mn²⁺. The activity with 4mM Mn²⁺ at pH 7.0-8.0 was almost the same as that with 30mM Mg²⁺. Changes in Km values for substrates and in susceptibility to inhibition by certain metabolites were observed when 30mM Mg²⁺ was replaced by 4mM Mn²⁺. Addition of a small amount of Co²⁺ greatly stimulated the reaction rate in the presence of a suboptimal level of Mg²⁺. Optimum pH, Km values for substrates and the inhibitory effect of metabolites were also changed in the mixture of Mg²⁺ and Co²⁺. Glutamine synthetase was reactive toward hydroxylamine, methylamine and ethylamine under the standard conditions as well as toward ammonia, and similarly the kinetics of these reactions were altered by divalent cations. The reaction products, γ-glutamyl derivatives, were identified.

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