CONVERSION OF AMMONIA TO AMINO GROUPS IN ESCHERICHIA COLI

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Abstract
Aspartase and triphosphopyridine nucleotide-linked glutamic dehydrogenase activities were determined in extracts of E. coli grown in mineral salts media containing various C sources. When glucose was the C source, the level of glutamic dehydrogenase appeared to be sufficiently high to account for the conversion of ammonia to amino groups. Aspartase activity in glucose-grown cells appeared to be too low to contribute significantly to ammonia assimilation. When either succinate or [alpha]-ketoglutarate was the C source, aspartase activity was about equal to that of glutamic dehydrogenase and, under these conditions, may have contributed to amino group formation. Aspartase activity was significantly higher than glutamic dehydrogenase activity when either glutamate or casein hydrolysate was the C source. This observation suggested that aspartase was more important than glutamic dehydrogenase in the conversion of amino groups to ammonia (a step essential for the use of amino acids as C sources).