Significance This report shows that the reducing power in the environment influences oxidation of glutamate in a neuronal tissue. Glutamate is a neurotransmitter, and it is especially important as a metabolite because it is required for synthesis of glutathione, other amino acids, and proteins. Glutamate also is a key intermediate in glutamine-dependent anaplerosis, now considered to be a principal source of citric acid cycle intermediates in cancer cells. Our analyses also show that the reducing power in the environmental can influence glutamate oxidation in cancer cells.