✍ Scribed by Kr�mer, Johannes
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Hydrogenomonas H 16 synthetized two chromatographically distinct forms of glutamate dehydrogenase which differed in their thermolability. One glutamate dehydrogenase utilized NAD, the other NADP as a coenzyme.
Low specific activity of NAD-dependent glutamate dehydrogenase was found in cells grown with glutamate as sole nitrogen source or in ceils grown with a high concentration of ammonium ions. In the presence of a low concentration of ammonium ions or in a nitrogen free medium, the specific activity of the NAD-dependent enzyme increased. Corresponding to the formation of the NAD-dependent glutamate dehydrogenase the enzyme glutamine synthetase was synthesized. The ratio of NAD-dependent glutamate dehydrogenase to glutamine synthetase activity differed only slightly in cells grown with different nitrogen and carbon sources.
The NADP-dependent glutamate dehydrogenase was found in high specific activity in cells grown with an excess of ammonium ions. Under nitrogen starvation the formation of the NADP-dependent glutamate dehydrogenase ceased and the enzyme activity decreased.
Only one distinct type of glutamate dehydrogenase specific for either NAD 1, NADP, or for both coenzymes is present in most bacteria, higher plants, and animals (Frieden, 1965). However, two different glutamate dehydrogenases, one utilizing NAD and the other IqADP as a coenzyme, have been demonstrated in several species of fungi (Holzer and Schneider,
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