On the utilization of L-glutamine by glutamate dehydrogenase.

The action of glutamate dehydrogenase on L-glutamine was followed by determining the formation of α-ketoglutaramate. The rate of the reaction with L-glutamine was about 0.01% of that observed with L-glutamate. The findings suggest that α-ketoglutaramate present in tissues arises mainly by transamination rather than by oxidation of glutamine. tamine. Glutamate dehydrogenase does not catalyze glutamate formation from α-ketoglutarate and L-glutamine at a significant rate, but the present findings do not exclude the possibility that glutamine amide nitrogen is used for synthesis of α-amino groups in the mammal by pathways involving coupling between glutamate dehydrogenase and glutaminase (or $\text{Ω-amidase}$) or a glutamine-binding subunit, i.e., by reactions equivalent to that catalyzed by glutamate synthase.